ORIGINAL CONTRIBUTION paroxysmal supraventricular tachycardia, verapamil; verapamil, paroxysmal supraventricular tachycardia
Intravenous Verapamil in the Prehospital Treatment of Paroxysmal Supraventricular Tachycardia The prehospital treatment of paroxysmal supraventricular tachycardia (PSVT) with verapamil alone or in comparison with other interventions has not been studied. A sequential protocol consisting of Valsalva maneuver, ice packs, pneumatic antishock garment inflation, and verapamil 0.5 mg IV was implemented in an urban emergency medical services system after appropriate paramedic education. On-line physician discretion could alter the protocol in specific clinical situations. Inclusion criteria required a narrow-complex regular tachycardia at a rate of between 150 and 250. Of 43 patients identified, the protocol was applied sequentially in 26 (60%) and with valid physician discretion in 15 patients (35%) (due to hypotension, chest pain, or dyspnea). Conversion to a more stable rhythm occurred in 25 patients (59%). Of these, all but one achieved a sinus mechanism. The Valsalva maneuver and ice pack application were ineffective in achieving rhythm conversion, being successful in only two of 33 (6%), one of 3i (3%), and four of 24 (17%) attempts, respectively (P > .05). Verapamil, however, was significantly more effective (18 of 24 attempts, 75%) than any of the other interventions either singly (P < .01) or in combination (P < .0001). No clinically important adverse effects occurred with any intervention, but application of the protocol increased mean on-scene time to 30.6 minutes. We conclude that verapamil is an effective agent for the prehospital termination of PSVT but that careful on-line physician supervision and a system for confirming rhythm identification are both essential. [O'Toole KS, Heller MB, Menegazzi J], Paris PM: Intravenous verapamil in the prehospital treatment of p a r o x y s m a l supraventricular tachycardia. Ann Emerg Med March 1990;19:291-294.]
Kevin S O'Toole, MD* Michael B Heller, MD* James J Menegazzi, PhDt Paul M Paris, MD* Pittsburgh, Pennsylvania From the Division of Emergency Medicine, University of Pittsburgh School of Medicine;* and the Center for Emergency Medicine,l- Pittsburgh, Pennsylvania. Received for publication September 17, 1986. Revision received July 27, 1989. Accepted for publication October 5, 1989. Presented at the Scientific Assembly of the American College of Emergency Physicians in Atlanta, September 1986. Address for reprints: Michael B Heller, MD, 230 McKee Place, Suite 500, Pittsburgh, Pennsylvania 15213.
INTRODUCTION The list of possible treatments for paroxysmal supraventricular tachycardia (PSVT) is long and variedJ -z Vagal maneuvers, pneumatic antishock garment (PASG), overdrive pacing, synchronous cardioversion, and numerous drugs have been used with varying degrees of success. With the release of IV verapamil in 1981, an effective treatment was added to the therapeutic arsenal. Several in-hospital studies have shown verapamil to be successful in terminating PSVT in 70% to m o r e than 90% of patients, S lz but the agent has never been studied in the prehospital setting. In addition to its undisputed efficacy, few clinically significant complications have been reported when verapamil was used appropriately. In the absence of any published prospective or comparative study of PSVT therapy, we developed a protocol that included several recognized treatments for PSVT: vagal stimulation by Valsalva maneuver, stimulation of the so-called "diving reflex" by application of chemical cold packs, PASG inflation, and finally, IV verapamil as a therapeutic option. METHODS Our study took place in an urban emergency medical services (EMS) system. Ours is a third-service system that operates 16 advanced life support (ALS) units. All ALS interventions carried out by paramedics are under direct radio supervision by a physician, who is an emergency medicine resident or faculty member at the University of Pittsburgh. All paramedics within the system as well as EMS physicians were instructed in the use of
19:3 March 1990
Annals of Emergency Medicine
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IV VERAPAMIL O'Toole et al
the protocol, and all were given a proficiency examination. The examination consisted of multiple-choice questions concerning verapamil, its pharmacology, and side effects as well as r h y t h m identification. The paramedics also were tested on the contraindications to the use of verapamil. Each patient treated for PSVT using the protocol had a study data sheet completed by the EMS physician. The paramedic trip sheet and the m a n d a t o r y ECG r h y t h m strips were collected for each patient. Patients of both sexes and all ages were eligible for the study. PSVT, for the purpose of this study, was defined as a regular rhythm with a rate between 150 and 250 and with a QRS duration of less than 120 ms. University of Pittsburgh institutional review board approval was obtained. Our protocol was designed to have two possible treatment groups. Stable patients with PSVT were treated with the sequential portion of the protocol. Patients with severe chest pain or shortness of breath, decreased mental status, or systolic blood pressure of less than 90 m m Hg were treated in the physician discretion portion of the protocol, but there were no predefined exclusion criteria other than known hypersensitivity to the verapami] and medical contraindication to the use of the PASG. Treatment options for this group of patients were decided on by the medical c o m m a n d physician, based on the patient's condition. First, in an awake patient with PSVT, oxygen therapy (6 L/rain by nasal cannula) was initiated. Second, an IV line of 50% dextrose in water at a keep-open rate was established before physician consultation. Third, a medical report was given to the on-line physician by radio for implementation of the protocol. Fourth, the Valsalva maneuver was performed and maintained for ten seconds by the patient after instruction by the paramedics. This was repeated once if necessary. Fifth, if the Valsalva maneuver was unsuccessful, two chemical ice packs were applied to cover the entire face. They were left in place for 30 seconds or removed earlier if the PSVT converted. Sixth, if ice packs failed to convert the rhythm, PASG was applied and all three chambers were inflated rap116/292
idly until the Velcro ® fasteners began to pull apart. If unsuccessful after three minutes, the PASG could be deflated in the standard fashion unless the patient was initially hypotensive, in which case it would remain inflated. Pulmonary edema and pregnancy were considered contraindicators to the use of PASG. Finally, if all the above measures failed to convert the PSVT and the systolic blood pressure was more than 90 m m Hg, 5 mg IV verapamil were given over one minute. A second 5-rag dose was administered on physician order in five minutes if normal sinus rhythm did not result after the first dose. If at any time during the protocol, the patient became unconscious, synchronized cardioversion with 50 J was performed. Physician consultation was obtained immediately after the attempted cardioversion. Any patient thought to be unstable by the c o m m a n d p h y s i c i a n was treated in the physician discretion portion of the protocol. The therapy given was decided on by the physician after evaluation of the patient's complaints, vital signs, and mental status. Descriptive statistics and perc e n t a g e s are p r e s e n t e d b e l o w . Fisher's exact test was used for all comparisons. The alpha error rate was set at 0.05.
RESULTS D u r i n g the s t u d y period, paramedics initially identified 58 cases of PSVT. Of these, 46 were judged to be actual PSVT by a three-physician panel. Three of these patients spontaneously converted to a sinus rhythm before application of the protocol; the r e m a i n i n g 43 c o m p r i s e d the study group. Misidentified rhythms included six sinus tachycardias, five atrial fibrillations with rapid conduction, and one case of ventricular tachycardia. The ventricular tachycardia was eventually identified correctly by the paramedics and treated appropriately. None of the patients in w h o m r h y t h m s were misidentified evidenced any deleterious effects attributable to the protocol. The patients averaged 55.2 years old (SD, 16.8 years; range, 11 to 80 years). Twenty-seven patients (63%) were female. The sequential portion of the protocol was applied to 26 of the 43 patients (60%). Valid physician discretion management occurred Annals of Emergency Medicine
in 15 patients (35%). Reasons for the use of physician discretion included systolic blood pressure of less than 90 m m Hg (seven patients), chest pain (five patients), and severe shortness of breath (three patients). In two patients (5%), the protocol was broken at the patient's discretion; one had the ice p a c k s r e m o v e d prematurely secondary to discomfort, and another refused placement of the PASG. This gave a protocol compliance rate of 95%. C o n v e r s i o n to a m o r e s t a b l e rhythm in the field occurred in 25 patients (59%). Of these, 24 (96%) converted to a sinus rhythm (including 13 sinus tachycardias and one sinus bradycardia). The one patient who failed to convert to a sinus rhythm converted to atrial fibrillation. The various c o m p o n e n t s of the protocol, how often each was used, and the conversion rate for each are shown (Table). Valsalva maneuver and ice packs proved to be relatively ineffective, converting only two and one patients, respectively (5% of 64 applications). PASG resulted in four conversions (17%) on patients in whom it was used. The rates of conversion for these three methods were n o t s t a t i s t i c a l l y s i g n i f i c a n t . VeraPamil resulted in 18 conversions (75); four of these patients received a second dose of the drug after failing to convert in the first five minutes. All of these converted after the second dose. The rate of conversion for verapamil was statistically different (P < .01) from each of the other three methods. It was also significantly different (P < .01) from the conversion rate for all three m e t h o d s combined (18 vs seven conversions). The success rate for the sequential protocol versus those treated by physician discretion were not significantly different (P = .59). The patients were transported to multiple EDs, and no a t t e m p t was made to d e t e r m i n e eventual outcome. One patient required cardioversion at 100 and 200 J without change in r h y t h m . No further i n t e r v e n t i o n s were reported on this patient. One of 24 patients (4%) receiving verapamil without conversion of her rhythm had an initial blood pressure drop from 80 systolic to 60 m m Hg s y s t o l i c . T h e b l o o d p r e s s u r e remained at this level throughout the prehospital period, and she did not 19:3 March 1990
TABLE. Conversion of PSVT with protocol elements Protocol Element
No. of Patients (%) Conversion (%) 33 (77) 2/33 (6) 31 (72) 1131 (3) PASG 24 (56) 4/24 (17) Verapamil 24 (56) 18/24 (75)* *P < .01 verapamil versus any single element; P < .0001 verapamil versus any combination of elements. Fisher's exact test. Valsalva maneuver Ice packs
receive a second dose. Due to her initial hypotension (systolic blood pressure of less than 90 m m Hg), she was validly assigned to the physician discretion portion of the protocol. There was no apparent deterioration in clinical condition. One of 24 patients (4%) reported discomfort from the PASG. Another refused the PASG as she had had them applied once before in the study and found them uncomfortable; she was the only patient in the study to be treated more than once. On-scene time for field teams cartying out the protocol was 30.6 minutes; the range of times was seven to 62 minutes. Time on scene is reported as time from arrival of ambulance to time en route with patient; this time includes finding the patient, taking a history and doing a physical examination, treating the patient, packaging for transport, and m o v i n g the patient to the ambulance. In our system, on-scene time for cases requiring ALS is 23.5 minutes.
DISCUSSION Various maneuvers, procedures, and drugs have been used in the t r e a t m e n t of PSVT. 1-7 Verapamil, w h e n used for properly identified PSVT, has been found to be both safe and effective in numerous hospital studies. 8-H This study, however, is the first reported study on its use in the prehospital setting and documents its efficacy. Our protocol was deliberately designed to m i n i m i z e the possibility that ventricular tachycardia would be inadvertently treated with measures intended for PSVT. We chose a QRS duration of less than 120 ms to avoid the misidentification of ventricular tachycardia as PSVT with aberrant conduction. Stewart and colleagues in Seattle have recently reported a se19:3 March 1990
ties of p a t i e n t s w i t h v e n t r i c u l a r tachycardia who were misdiagnosed by physicians as having PSVT. ~3 All of the misdiagnosed patients who were treated w i t h v e r a p a m i l had poorer outcomes, and this was attributed to the verapamil. One patient in our series with ventricular tachycardia was initially misdiagnosed but not given verapamil. Because all four patients who received a second dose of verapamil converted to a more stable rhythm, it is possible that an even higher success rate could be obtained with more aggressive therapy. Rhythm misidentification must rem a i n a concern. Twelve patients (21%) were initially interpreted by paramedics to be in PSVT when they were not. Our EMS system does not use telemetry; the medical command physicians were not aware of the misidentification when treatment orders were given. The five patients found to be in rapid atrial fibrillation could theoretically have been h a r m e d if treated with verapamil while having a pre-excitation syndrome as a verapamil-induced increase in ventricular response in this s y n d r o m e has been reported. Of course, treatment of rapid atrial fibrillation with verapamil may also be beneficial) 4 On investigation into the misidentification, it was discovered that many field personnel were attempting to provide both r h y t h m s and rates from the screen of the monitor. We now mandate that an ECG strip be obtained to determine rate and that calipers are used to document regularity and QRS duration in every case. Particularly in systems without telemetry, our experience indicates that such a policy is necessary if prehospital rhythm conversion is to be attempted. Several complications of therapy in Annals of Emergency Medicine
our study deserve mention. Hypotension is a well-recognized effect of many calcium channel blockers, and the elderly patient who received verapamil with a systolic blood pressure of 80 m m Hg had an asymptomatic drop in pressure to 60 m m Hg. Verapamil use is controversial in such patients, although hypotension is not an absolute contraindication in the person whose low blood pressure is believed to be secondary to the rapid rate. Recently, it has been noted that IV calcium given before verapamil administration may obviate this problem, 15 but careful pat i e n t s e l e c t i o n is required if verapamil is to be considered in the setting of hypotension. Certainly, the known risks of such treatment in the prehospital environment may often outweigh the potential benefits. Our prolonged time-on-scene (one third longer than the mean ALS time in the Pittsburgh EMS) may reflect the application of a multistep study protocol. From the perspective of time effectiveness, it could be argued that the most successful therapy, verapamil, should be carried out rather promptly and that one or both of the more time-consuming and less-effective treatments (PASG and ice packs) should not be used routinely before instituting transport. The fact that the conversion rates for the sequential protocol versus physician discretion group were not significantly different supports this strategy, as does the fact the combined conversion rate for the three nonpharmacologic i n t e r v e n t i o n s (Valsalva maneuver, ice packs, and PASG) was only one third that of the verapamil group. CONCLUSION IV verapamil has a significantly higher success rate than any combination of the Valsalva maneuver, ice packs, and PASG for the conversion of PSVT to a more stable rhythm in the field setting. No major adverse effects were noted with any of the interventions, although rhythm misidentification was frequent. Verapamil appears to be a useful prehospital agent, but a secure system for rhythm identification must be established before its use. In addition, on-line physician consultation, both for rhythm confirmation and as an aid in patient selection, would seem necessary if this agent is to be used safely. As with many ALS inter293/117
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ventions, the ratio of risk to benefit for prehospital rhythm conversion of PSVT is not clear and will no doubt vary according to each EMS system.
REFERENCES l. Kuhn M: Verapamil in the treatment of atrial fibrillation or flutter tachycardia. Digest Emerg Med Gare 1982;2:1-6. 2. Tandberg D, Rusnak R, Sklar D, et al: Successful treatment of paroxysmal supraventricular taehycardia with MAST. Ann Emerg Med 1984;13:1068-1070. 3. Waxman B, Wald R, Sharma AD, et al: Vagal techniques for termination of paroxysmal supraventrieular tachycardia. A m J Cardiol 1980; 46:655-664. 4. Bisset G, Gaum W, Kaplan S: The ice bag: A n e w t e c h n i q u e for i n t e r r u p t i o n of supra-
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ventricular tachycardia. J Pediatr 1980;97: 593-595. 5. Schamroth L: Verapamil: Recommendations and caveats. J Cardiovasc 1984;9:206-214. 6. Morady F, Scheinman M: Paroxysmal supraventricular tachycardia: Part II. Treatment. Mod Concepts Cardiovasc Dis 198~Z;51:l13q17. 7. Josephson M, Kastor J: Supraventricular tachycardia: Mechanisms and management. Ann Intern Mecl 1977;87:346-358. 8. Schamroth L: The clinical use of intravenous verapamil. A m Heart J 1980;100:1070-1075.
1981;94:1-6. ll. Rinkenberger RL, Prystowsky EN, Heger JJ, et al: Effects of intravenous and chronic oral verapamil in patients with supraventricular tachyarrhythmias. Circulation 1980;62:996-1010. 12. Kuhn M: Verapamil in the treatment of PSVT. Ann Em~rg Med 1981;10:538-544. 13. Stewart R, Bardy G, Greene H: Wide complex tachycardia: Misdiagnosis and outcome after e m e r g e n t t h e r a p y . A n n f n t e r n M e d 1986; 104: 766- 771.
9. Gonzalez R, Scheinman M: Treatment of su ~ praventricutar arrhythmias with intravenous and oral verapamil. Chest 1981;80:465-470.
14. McGovern B, Garan H, Ruskin J: Precipitation of cardiac arrest by verapamil in patients with Wolf-Parkinson-White syndrome. Ann Intern Med 1986;104:791-794,
10. Waxman HL, Myerburg RJ, Appel R, et al: Verapamil for control of ventricular rate in paroxysmal supraventricular taehycardia and atrial f i b r i l l a t i o n or f l u t t e r . A n n I n t e r n M e d
15. Haft J, Habbab M: Treatment of atrial arrhythmias: Effectiveness of verapamil w h e n preceded by calcium infusion. Arch Intern 1986;146:1085-1089.
Annals of Emergency Medicine
19:3 March 1990
Intravenous Verapamil in the Prehospital Treatment of Paroxysmal Supraventricular Tachycardia The prehospital treatment of paroxysmal supraventricular tachycardia (PSVT) with verapamil alone or in comparison with other interventions has not been studied. A sequential protocol consisting of Valsalva maneuver, ice packs, pneumatic antishock garment inflation, and verapamil 0.5 mg IV was implemented in an urban emergency medical services system after appropriate paramedic education. On-line physician discretion could alter the protocol in specific clinical situations. Inclusion criteria required a narrow-complex regular tachycardia at a rate of between 150 and 250. Of 43 patients identified, the protocol was applied sequentially in 26 (60%) and with valid physician discretion in 15 patients (35%) (due to hypotension, chest pain, or dyspnea). Conversion to a more stable rhythm occurred in 25 patients (59%). Of these, all but one achieved a sinus mechanism. The Valsalva maneuver and ice pack application were ineffective in achieving rhythm conversion, being successful in only two of 33 (6%), one of 3i (3%), and four of 24 (17%) attempts, respectively (P > .05). Verapamil, however, was significantly more effective (18 of 24 attempts, 75%) than any of the other interventions either singly (P < .01) or in combination (P < .0001). No clinically important adverse effects occurred with any intervention, but application of the protocol increased mean on-scene time to 30.6 minutes. We conclude that verapamil is an effective agent for the prehospital termination of PSVT but that careful on-line physician supervision and a system for confirming rhythm identification are both essential. [O'Toole KS, Heller MB, Menegazzi J], Paris PM: Intravenous verapamil in the prehospital treatment of p a r o x y s m a l supraventricular tachycardia. Ann Emerg Med March 1990;19:291-294.]
Kevin S O'Toole, MD* Michael B Heller, MD* James J Menegazzi, PhDt Paul M Paris, MD* Pittsburgh, Pennsylvania From the Division of Emergency Medicine, University of Pittsburgh School of Medicine;* and the Center for Emergency Medicine,l- Pittsburgh, Pennsylvania. Received for publication September 17, 1986. Revision received July 27, 1989. Accepted for publication October 5, 1989. Presented at the Scientific Assembly of the American College of Emergency Physicians in Atlanta, September 1986. Address for reprints: Michael B Heller, MD, 230 McKee Place, Suite 500, Pittsburgh, Pennsylvania 15213.
INTRODUCTION The list of possible treatments for paroxysmal supraventricular tachycardia (PSVT) is long and variedJ -z Vagal maneuvers, pneumatic antishock garment (PASG), overdrive pacing, synchronous cardioversion, and numerous drugs have been used with varying degrees of success. With the release of IV verapamil in 1981, an effective treatment was added to the therapeutic arsenal. Several in-hospital studies have shown verapamil to be successful in terminating PSVT in 70% to m o r e than 90% of patients, S lz but the agent has never been studied in the prehospital setting. In addition to its undisputed efficacy, few clinically significant complications have been reported when verapamil was used appropriately. In the absence of any published prospective or comparative study of PSVT therapy, we developed a protocol that included several recognized treatments for PSVT: vagal stimulation by Valsalva maneuver, stimulation of the so-called "diving reflex" by application of chemical cold packs, PASG inflation, and finally, IV verapamil as a therapeutic option. METHODS Our study took place in an urban emergency medical services (EMS) system. Ours is a third-service system that operates 16 advanced life support (ALS) units. All ALS interventions carried out by paramedics are under direct radio supervision by a physician, who is an emergency medicine resident or faculty member at the University of Pittsburgh. All paramedics within the system as well as EMS physicians were instructed in the use of
19:3 March 1990
Annals of Emergency Medicine
291/115
IV VERAPAMIL O'Toole et al
the protocol, and all were given a proficiency examination. The examination consisted of multiple-choice questions concerning verapamil, its pharmacology, and side effects as well as r h y t h m identification. The paramedics also were tested on the contraindications to the use of verapamil. Each patient treated for PSVT using the protocol had a study data sheet completed by the EMS physician. The paramedic trip sheet and the m a n d a t o r y ECG r h y t h m strips were collected for each patient. Patients of both sexes and all ages were eligible for the study. PSVT, for the purpose of this study, was defined as a regular rhythm with a rate between 150 and 250 and with a QRS duration of less than 120 ms. University of Pittsburgh institutional review board approval was obtained. Our protocol was designed to have two possible treatment groups. Stable patients with PSVT were treated with the sequential portion of the protocol. Patients with severe chest pain or shortness of breath, decreased mental status, or systolic blood pressure of less than 90 m m Hg were treated in the physician discretion portion of the protocol, but there were no predefined exclusion criteria other than known hypersensitivity to the verapami] and medical contraindication to the use of the PASG. Treatment options for this group of patients were decided on by the medical c o m m a n d physician, based on the patient's condition. First, in an awake patient with PSVT, oxygen therapy (6 L/rain by nasal cannula) was initiated. Second, an IV line of 50% dextrose in water at a keep-open rate was established before physician consultation. Third, a medical report was given to the on-line physician by radio for implementation of the protocol. Fourth, the Valsalva maneuver was performed and maintained for ten seconds by the patient after instruction by the paramedics. This was repeated once if necessary. Fifth, if the Valsalva maneuver was unsuccessful, two chemical ice packs were applied to cover the entire face. They were left in place for 30 seconds or removed earlier if the PSVT converted. Sixth, if ice packs failed to convert the rhythm, PASG was applied and all three chambers were inflated rap116/292
idly until the Velcro ® fasteners began to pull apart. If unsuccessful after three minutes, the PASG could be deflated in the standard fashion unless the patient was initially hypotensive, in which case it would remain inflated. Pulmonary edema and pregnancy were considered contraindicators to the use of PASG. Finally, if all the above measures failed to convert the PSVT and the systolic blood pressure was more than 90 m m Hg, 5 mg IV verapamil were given over one minute. A second 5-rag dose was administered on physician order in five minutes if normal sinus rhythm did not result after the first dose. If at any time during the protocol, the patient became unconscious, synchronized cardioversion with 50 J was performed. Physician consultation was obtained immediately after the attempted cardioversion. Any patient thought to be unstable by the c o m m a n d p h y s i c i a n was treated in the physician discretion portion of the protocol. The therapy given was decided on by the physician after evaluation of the patient's complaints, vital signs, and mental status. Descriptive statistics and perc e n t a g e s are p r e s e n t e d b e l o w . Fisher's exact test was used for all comparisons. The alpha error rate was set at 0.05.
RESULTS D u r i n g the s t u d y period, paramedics initially identified 58 cases of PSVT. Of these, 46 were judged to be actual PSVT by a three-physician panel. Three of these patients spontaneously converted to a sinus rhythm before application of the protocol; the r e m a i n i n g 43 c o m p r i s e d the study group. Misidentified rhythms included six sinus tachycardias, five atrial fibrillations with rapid conduction, and one case of ventricular tachycardia. The ventricular tachycardia was eventually identified correctly by the paramedics and treated appropriately. None of the patients in w h o m r h y t h m s were misidentified evidenced any deleterious effects attributable to the protocol. The patients averaged 55.2 years old (SD, 16.8 years; range, 11 to 80 years). Twenty-seven patients (63%) were female. The sequential portion of the protocol was applied to 26 of the 43 patients (60%). Valid physician discretion management occurred Annals of Emergency Medicine
in 15 patients (35%). Reasons for the use of physician discretion included systolic blood pressure of less than 90 m m Hg (seven patients), chest pain (five patients), and severe shortness of breath (three patients). In two patients (5%), the protocol was broken at the patient's discretion; one had the ice p a c k s r e m o v e d prematurely secondary to discomfort, and another refused placement of the PASG. This gave a protocol compliance rate of 95%. C o n v e r s i o n to a m o r e s t a b l e rhythm in the field occurred in 25 patients (59%). Of these, 24 (96%) converted to a sinus rhythm (including 13 sinus tachycardias and one sinus bradycardia). The one patient who failed to convert to a sinus rhythm converted to atrial fibrillation. The various c o m p o n e n t s of the protocol, how often each was used, and the conversion rate for each are shown (Table). Valsalva maneuver and ice packs proved to be relatively ineffective, converting only two and one patients, respectively (5% of 64 applications). PASG resulted in four conversions (17%) on patients in whom it was used. The rates of conversion for these three methods were n o t s t a t i s t i c a l l y s i g n i f i c a n t . VeraPamil resulted in 18 conversions (75); four of these patients received a second dose of the drug after failing to convert in the first five minutes. All of these converted after the second dose. The rate of conversion for verapamil was statistically different (P < .01) from each of the other three methods. It was also significantly different (P < .01) from the conversion rate for all three m e t h o d s combined (18 vs seven conversions). The success rate for the sequential protocol versus those treated by physician discretion were not significantly different (P = .59). The patients were transported to multiple EDs, and no a t t e m p t was made to d e t e r m i n e eventual outcome. One patient required cardioversion at 100 and 200 J without change in r h y t h m . No further i n t e r v e n t i o n s were reported on this patient. One of 24 patients (4%) receiving verapamil without conversion of her rhythm had an initial blood pressure drop from 80 systolic to 60 m m Hg s y s t o l i c . T h e b l o o d p r e s s u r e remained at this level throughout the prehospital period, and she did not 19:3 March 1990
TABLE. Conversion of PSVT with protocol elements Protocol Element
No. of Patients (%) Conversion (%) 33 (77) 2/33 (6) 31 (72) 1131 (3) PASG 24 (56) 4/24 (17) Verapamil 24 (56) 18/24 (75)* *P < .01 verapamil versus any single element; P < .0001 verapamil versus any combination of elements. Fisher's exact test. Valsalva maneuver Ice packs
receive a second dose. Due to her initial hypotension (systolic blood pressure of less than 90 m m Hg), she was validly assigned to the physician discretion portion of the protocol. There was no apparent deterioration in clinical condition. One of 24 patients (4%) reported discomfort from the PASG. Another refused the PASG as she had had them applied once before in the study and found them uncomfortable; she was the only patient in the study to be treated more than once. On-scene time for field teams cartying out the protocol was 30.6 minutes; the range of times was seven to 62 minutes. Time on scene is reported as time from arrival of ambulance to time en route with patient; this time includes finding the patient, taking a history and doing a physical examination, treating the patient, packaging for transport, and m o v i n g the patient to the ambulance. In our system, on-scene time for cases requiring ALS is 23.5 minutes.
DISCUSSION Various maneuvers, procedures, and drugs have been used in the t r e a t m e n t of PSVT. 1-7 Verapamil, w h e n used for properly identified PSVT, has been found to be both safe and effective in numerous hospital studies. 8-H This study, however, is the first reported study on its use in the prehospital setting and documents its efficacy. Our protocol was deliberately designed to m i n i m i z e the possibility that ventricular tachycardia would be inadvertently treated with measures intended for PSVT. We chose a QRS duration of less than 120 ms to avoid the misidentification of ventricular tachycardia as PSVT with aberrant conduction. Stewart and colleagues in Seattle have recently reported a se19:3 March 1990
ties of p a t i e n t s w i t h v e n t r i c u l a r tachycardia who were misdiagnosed by physicians as having PSVT. ~3 All of the misdiagnosed patients who were treated w i t h v e r a p a m i l had poorer outcomes, and this was attributed to the verapamil. One patient in our series with ventricular tachycardia was initially misdiagnosed but not given verapamil. Because all four patients who received a second dose of verapamil converted to a more stable rhythm, it is possible that an even higher success rate could be obtained with more aggressive therapy. Rhythm misidentification must rem a i n a concern. Twelve patients (21%) were initially interpreted by paramedics to be in PSVT when they were not. Our EMS system does not use telemetry; the medical command physicians were not aware of the misidentification when treatment orders were given. The five patients found to be in rapid atrial fibrillation could theoretically have been h a r m e d if treated with verapamil while having a pre-excitation syndrome as a verapamil-induced increase in ventricular response in this s y n d r o m e has been reported. Of course, treatment of rapid atrial fibrillation with verapamil may also be beneficial) 4 On investigation into the misidentification, it was discovered that many field personnel were attempting to provide both r h y t h m s and rates from the screen of the monitor. We now mandate that an ECG strip be obtained to determine rate and that calipers are used to document regularity and QRS duration in every case. Particularly in systems without telemetry, our experience indicates that such a policy is necessary if prehospital rhythm conversion is to be attempted. Several complications of therapy in Annals of Emergency Medicine
our study deserve mention. Hypotension is a well-recognized effect of many calcium channel blockers, and the elderly patient who received verapamil with a systolic blood pressure of 80 m m Hg had an asymptomatic drop in pressure to 60 m m Hg. Verapamil use is controversial in such patients, although hypotension is not an absolute contraindication in the person whose low blood pressure is believed to be secondary to the rapid rate. Recently, it has been noted that IV calcium given before verapamil administration may obviate this problem, 15 but careful pat i e n t s e l e c t i o n is required if verapamil is to be considered in the setting of hypotension. Certainly, the known risks of such treatment in the prehospital environment may often outweigh the potential benefits. Our prolonged time-on-scene (one third longer than the mean ALS time in the Pittsburgh EMS) may reflect the application of a multistep study protocol. From the perspective of time effectiveness, it could be argued that the most successful therapy, verapamil, should be carried out rather promptly and that one or both of the more time-consuming and less-effective treatments (PASG and ice packs) should not be used routinely before instituting transport. The fact that the conversion rates for the sequential protocol versus physician discretion group were not significantly different supports this strategy, as does the fact the combined conversion rate for the three nonpharmacologic i n t e r v e n t i o n s (Valsalva maneuver, ice packs, and PASG) was only one third that of the verapamil group. CONCLUSION IV verapamil has a significantly higher success rate than any combination of the Valsalva maneuver, ice packs, and PASG for the conversion of PSVT to a more stable rhythm in the field setting. No major adverse effects were noted with any of the interventions, although rhythm misidentification was frequent. Verapamil appears to be a useful prehospital agent, but a secure system for rhythm identification must be established before its use. In addition, on-line physician consultation, both for rhythm confirmation and as an aid in patient selection, would seem necessary if this agent is to be used safely. As with many ALS inter293/117
IV VERAPAMIL O'Toole et al
ventions, the ratio of risk to benefit for prehospital rhythm conversion of PSVT is not clear and will no doubt vary according to each EMS system.
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ventricular tachycardia. J Pediatr 1980;97: 593-595. 5. Schamroth L: Verapamil: Recommendations and caveats. J Cardiovasc 1984;9:206-214. 6. Morady F, Scheinman M: Paroxysmal supraventricular tachycardia: Part II. Treatment. Mod Concepts Cardiovasc Dis 198~Z;51:l13q17. 7. Josephson M, Kastor J: Supraventricular tachycardia: Mechanisms and management. Ann Intern Mecl 1977;87:346-358. 8. Schamroth L: The clinical use of intravenous verapamil. A m Heart J 1980;100:1070-1075.
1981;94:1-6. ll. Rinkenberger RL, Prystowsky EN, Heger JJ, et al: Effects of intravenous and chronic oral verapamil in patients with supraventricular tachyarrhythmias. Circulation 1980;62:996-1010. 12. Kuhn M: Verapamil in the treatment of PSVT. Ann Em~rg Med 1981;10:538-544. 13. Stewart R, Bardy G, Greene H: Wide complex tachycardia: Misdiagnosis and outcome after e m e r g e n t t h e r a p y . A n n f n t e r n M e d 1986; 104: 766- 771.
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10. Waxman HL, Myerburg RJ, Appel R, et al: Verapamil for control of ventricular rate in paroxysmal supraventricular taehycardia and atrial f i b r i l l a t i o n or f l u t t e r . A n n I n t e r n M e d
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Annals of Emergency Medicine
19:3 March 1990
