ORIGINAL CONTRIBUTION
adenosine; paroxysmal supraveutricular tachycardia
Intravenous Adenosine in the Prehospital Treatmentof Paroxysmal SupraventricularTachycardia From the University of
James L McCabe, MD*
Pittsburgh Affiliated Residency
Gur C Adhar, MD ~
in Emergency Medicine;*
James J Menegazzi, PhD*
Electrophysiology Laboratory,
Paul M Paris, MD §
Study objective: To determine the clinical efficacy and safety of IV adenosine administration in the field for the treatment of paroxysmal supraventricular tachycardia (PSVT). Design: Prospective, consecutive case series.
The Mercy Hospital of Pittsburgh; t The Center for
Setting: An urban emergency medical services system.
Emergency Medicine of Western
P a r t i c i p a n t s : Thirty-seven adult patients in whom paramedics made
Pennsylvania; ¢ and Division of
the diagnosis of PSVT.
Emergency Medicine, University of Pittsburgh School of Medicine, § Pittsburgh, Pennsylvania. Received for publication May 14, 1991. Revision received July 1, 1991. Accepted for publication August 23, 1991. Presented at the Society for Academic Emergency Medicine Aunual Meeting in Washington, DC, May 1991. This study was funded in part by the Fujisawa Pharmaceutical Company and the Pittsburgh Emergency Medicine Foundation.
I n t e r v e n t i o n s : Six milligrams of adenosine was administered by
rapid IV bolus. If there was no effect within two minutes, a 12-mg bolus was given. This dose was repeated once if necessary. If there still was no effect, the medical command physician was contacted for further management. Measurements: Vital signs, symptoms, and a single-channel ECG were recorded before, during, and after the administration of adenosine. Results: On review of the ECG tracings, 26 patients (70%) were in PSVT. Eleven had rhythms other than PSVTon review, including five with atrial fibrillation, four with sinus tachycardia, and two with ventricular tachycardia. Of the 26 patients with PSVT,23 (88%) converted to sinus rhythm after adenosine administration. Eleven patients were hypotensive at presentation. Seven of these were in PSVTand became hemodynamically stable on conversion with adenosine. The four hypotensive patients with rhythms other than PSVT(two with atrial fibrillation and two with ventricular tachycardia) had no change in blood pressure after adenosine administration. Nine patients were subsequently found to have wide-complex tachycardia. None of these patients suffered hemodynamic compromise after adenosine administration, and side effects were infrequent, mild, and transient. Conclusion: Adenosine appears to be effective and safe for the prehospital treatment of PSVT. [McOabe JL, Adhar GC, Menegazzi J J, Paris PM: Intravenous adenosine in the prehospital treatment of paroxysmal supraventricular tachycardia. Ann EmergMedApri11992;21:358-361.]
20/358
ANNALS 0F EMERGENCYMEDICINE 21:4 APRIL1992
IV ADENOSINE McCabe et al
INTRODUCTION
MATERIALS AND METHODS
Paroxysmal supraventricular tachycardia (PSVT) is a commonly encountered dysrhythmia in the prehospital setting. Among the different types of PSVT, atrioventricular (AV) nodal re-entry and AV reciprocating tachycardia involving an accessory pathway account for the large majority and can be terminated by AV node blockade. 1 Current American H e a r t Association guidelines for the acute treatment of PSVT include vagal maneuvers and AV nodalblocking agents, such as digoxin, verapamil, and B-blockers, as well as synchronous electrical cardioversion in the unstable patient. 2 Theoretically, the prehospital treatment of PSVT should be the same; however, electrical cardioversion in this less-controlled setting should be used with caution. F u r t h e r m o r e , many emergency medical services (EMS) systems do not c a r r y verapamil. Adenosine is an endogenous nucleoside that produces transient AV nodal conduction delay after IV administration and thus is effective in terminating supraventricular tachycardias involving the AV node. 3 It has no direct effect on primary atrial dysrhythmias, including atrial fibrillation, atrial flutter, ectopic atrial tachycardia, and muhifocal atrial tachycardia. However, by slowing ventricular response, it can be useful in diagnosing these rhythms, a Other cardiac effects of adenosine include inhibition of sinus node automaticity and coronary artery vasodilatation. It is eliminated by active reuptake into cells and degradation by adenosine deaminase. Its half-life is approximately ten seconds. Because of such a short half-life, it is thought that adenosine exerts its effect during the first pass through the cardiac circulation and is most effective when given rapidly and close to the central circulation. Side effects are generally minor and include flushing, shortness of breath, chest pain, and lightheadedness. 3 Transient AV block, induced during the administration of adenosine, sometimes can be prolonged. P r e m a t u r e atrial, nodal, and ventricular beats are frequently seen during conversion but are rarely serious. All of these effects are transient and usually require no intervention. Adenosine does not significantly alter blood pressure, and to date there have been no reports of hemodynamic collapse associated with its use. Drug interactions include theophylline, which antagonizes its effects through receptor blockade, and dipyridamole, which enhances the effects of adenosine through inhibition of cellular reuptake. Although adenosine has been widely used in a controlled setting within the hospital, its use by paramedics in the prehospital setting has not been reported. The purpose of this investigation was to determine the clinical efficacy and safety of IV adenosine administration by paramedics in the field for the treatment of PSVT.
This investigation was a prospective, consecutive case series performed over a one-year period within the City of Pittsburgh EMS system. This is a single-tier system that operates 15 advanced life support units that receive on-line medical command from University of Pittsburgh emergency medicine residents and faculty. The annual call volume is approximately 60,000. Approval for the study was obtained from the HUman Rights Committee of the Western Pennsylvania Hospital and the State of Pennsylvania Department of Health, Division of Emergency Medical Services. Consecutive patients over the age of 18 years who were clinically diagnosed by paramedics as having PSVT were entered into the study. F o r the purpose of this study, PSVT was defined as a regular tachycardia at a rate between 150 and 250 beats p e r minute with a QRS duration of less than 120 ms. Patients were excluded if they had known hypersensitivity to adenosine or were in e x t r e m i s . After radio contact with a medical command physician, an IV line was placed in an antecubital vein, and 6 mg adenosine was administered as a r a p i d IV bolus; if there was no effect within two minutes, a 12-mg bolus was given. This dose was r e p e a t e d once if necessary. If there still was no response, no f u r t h e r adenosine was administered, and the medical command physician was recontacted to assist with f u r t h e r management. H e a r t rate, blood pressure, respirations, and symptoms were obtained before and after the administration of adenosine. Single-channel, continuous ECG tracings were obtained before, during, and after the administration of adenosine. The rhythm strips were subsequently reviewed by two of the investigators, one of whom was an electrophysiologist. In patients whose rhythms were not clearly determined by the prehospital rhythm strip, clinical information and 12-lead ECGs from the receiving hospital were used to assist in the diagnosis.
APRIL1992
21:4 ANNALS OF EMERGENCY MEDICINE
RESULTS Between March 1990 and April 1991, 37 consecutive p, ttients with a clinical diagnosis of PSVT received IV adenosin,~ in the field from paramedics. The mean age of patients in the study was 62 _+17 years; 20 were women. Fourteen patients (38%) had known structural heart disease. Based on subsequent review of ECG data, 26 of 37 patients (70%) met criteria for PSVT, five were in atrial fibrillation, four had sinus tachycardia, and two were in ventricular tachycardia. Twenty-three of the 26 patients in PSVT (88%) converted to sinus rhythm with adenosine. Of the three patients who did not convert, two were later found to have therapeutic levels of theophylline, and one received only a single 6-mg dose. The rhythm strips in the five patients in r a p i d atrial fibrillation initially a p p e a r e d regular; however, •
359/21
IV ADENOSINE M c C a b e et al
irregularity became a p p a r e n t as the ventricular response was transiently slowed with adenosine. Of the four patients in sinus tachycardia, three had no visible P waves on the prehospital strips but P waves were seen on subsequent 12lead ECGs. The fourth patient h a d first-degree AV block, and on review, P waves were seen b u r i e d within the p r i o r T wave. Adenosine caused transient sinus slowing in one of these patients and had no effect on the other three. Two patients were subsequently diagnosed as having VT. Adenosine had no effect on rhythm or blood pressure in either of these patients. At the receiving hospitals, one patient converted with lidocaine, and the other required electrical cardioversion. No adverse hemodynamic effects occurred in any patient receiving adenosine. Eleven patients were hypotensive (systolic blood pressure of 90 mm Hg or less) and had symptoms including chest pain, dyspnea, or lightheadedness on presentation. Seven of these with PSVT became hemodynamically stable after conversion to sinus r h y t h m with adenosine. The remaining four patients who were hypotensive and found to be in rhythms other than PSVT (including one patient with VT) exhibited no hemodynamic change with the administration of adenosine. On review, nine patients had a QRS duration of more than 120 ms and were diagnosed as having wide-complex tachycardia. Seven of these patients had pre-existing bundle b r a n c h blocks, two were in VT, and one r h y t h m was never clearly determined. None had hemodynamic deterioration with the administration of adenosine. Adverse effects occurred in six patients (16%), including two with flushing, two with chest pain, and one with dyspnea. One patient receiving dipyridamole at the time had a 3.6-second pause. All of these effects were transient and required no intervention. One patient (3%) had a recurrence of PSVT en route to the hospital.
DISCUSSION The results of this study demonstrate that adenosine is effective and safe in the prehospital treatment of PSVT. Although several rhythms were misinterpreted, adenosine was administered without harm. Presently, verapamil is the only pharmacologic treatment for PSVT a p p r o v e d for prehospital use. A recent multicenter, inpatient trial compared adenosine with verapamil in a prospective,
Figure. Termination of PSVT after adenosine
22/360
double-blind fashion and found the two to be equally effective in terminating PSVT. 5 Verapamil, however, has several characteristics that make it less desirable for use in the prehospital setting. It is a potent negative inotrope and vasodilator and can cause prolonged hypotension as well as precipitate acute congestive h e a r t failure. 6 Serious b r a d y d y s r h y t h m i a s and ventricular standstill can occur in patients on concomitant B-blocker therapy. Verapamil is known to have deleterious side effects in the setting of widecomplex tachycardia and can result in cardiac arrest if administered to a patient in VT. 6 It has also been shown to precipitate cardiac arrest when given to patients in atrial fibrillation with pre-excitation syndromes. 7 In contrast, adenosine does not cause any of these effects, and its extremely short half-life ensures p r o m p t resolution of any adverse effects. Adenosine has been given to patients in VT without adverse effect and has been shown to terminate catecholamine-induced VT. a'9 It also has been given to 14 patients with ventricular pre-excitation syndromes in atrial fibrillation without adverse effect. 10,11 There are two groups of patients in this study that deserve special mention. The first is the group of 11 patients who were hypotensive and symptomatic. The seven patients in PSVT were promptly converted to sinus rhythm with the administration of adenosine, which quickly restored hemodynamic stability. This precluded synchronous electrical cardioversion in these patients, which, although indicated in this situation, is much less desirable in the out-of-hospital setting, especially in the awake patient. This may have an impact on future advanced cardiac life support guidelines. The four hypotensive patients with rhythms other than PSVT f u r t h e r demonstrate adenosine's unique safety profile. The problems associated with the misdiagnosis and emergency treatment of wide-complex tachycardia have been well described. 12 Although our protocol was designed to include only narrow-complex tachycardia, a group of nine patients with a QRS duration of more than 120 ms were clinically diagnosed as having PSVT and were given adenosine. Two of them were in VT. Again, none of these patients developed any adverse hemodynamic effect. This experience is similar to that of two recently published investigations performed in electrophysiologic testing laboratories that have shown adenosine to be safe and effective in the diagnosis and treatment of wide-complex tachyeardia. 10,11 A previous prehospital investigation of PSVT in our system demonstrated a rhythm misidentification rate of 21%. 13 Since that time, paramedics have been required to r u n an ECG strip and use calipers to measure QRS regularity and duration. Despite this, the misidentification rate remains high, as demonstrated by our study, and further emphasizes the need for continuous ECG training as well as the limitation of single-channel ECG interpretation. •
ANNALS OF EMERGENCY MEDICINE 21:4 APRIL1992
IV ADENOSINE .~cCabe et al
CONCLUSION
REFERENCES
Adenosine is effective and safe for use by paramedics in the prehospital treatment of clinically diagnosed PSVT. It terminates PSVT in the majority of cases and is helpful in diagnosing other p r i m a r y atrial dysrhythmias. Based on a limited number of patients in this and other studies, l ° ' n adenosine appears to be safe in the setting of hypotension as well as wide-complex tachycardia. It may well preclude the prehospital use of verapamil for PSVT in the future and may also become an alternative to electrical cardioversion in the unstable patient who is not in e x t r e m i s . Future prehospital investigations could include a larger, muhicenter trial; a prospective evaluation of adenosine in patients with wide-complex t a c h y c a r d i a ; and use in the pediatric population. 14, is
1. Frame LN, Hoffman BF: Mechanisms of tachycardia, in Surawicz B (ed): Tachycardias. Boston, Martinus Nijhoff, 1984.
The authors thank the City of Pittsburgh p a r a m e d i c s , whose skill and cooperation made this study possible.
2. Standards and guidelines for cardiopulmonary resuscitation (CPR) and emergent cardiac care (ECC). JAMA 1986;255:2905. 3. DiMarco JP: Adenosine and supraventricular tachycardia, in Pelleg A, Michelson EL, Dreifus LS (ads): Cardiac Electrophysiology and Pharmacology of Adenosine and A TP: Basic and ClinicalAspects. New York, Alan R Liss, Inc, 1987, p 271-281. 4. BiMarco JP, Sellers TD, Lerman BB, et al: Diagnostic and therapeutic use of adenosine in patients with supraventricular tachyarrhythmias. JAm Coil Cardiol 1985;6:417-425. 5. DiMarco JP, Miles W, Akhtar M, et al: Adenosine for paroxysmal supraventricular tachycardia: Dose ranging and comparison to veraparnil. Ann Intern Med1990;113:104110. 6. Veraparnil for arrhythmias. MedLett1981;23:29-30. 7. McGovern B, Garan H, Ruskin JN: Precipitation of cardiac arrest by veraparnil in patients with Wolff-Parkinson-White syndrome. Ann Intern Med 1986;104:791-794. 8. Lerrnan BB, 8elardinelli L: Adenosine-sensitive ventricular tachycardia: Evidence suggesting cyclic AMP-mediated triggered activity. Circulation 1986;74:270-280. 9. Lerrnan BB, Be]ardinelli L: Effects of adenosine on ventricular tachycardia, in PeHeg A, Dreifus LS (eds): Cardiac Electrophysiology and Pharmacology of Adenosine and A TP: Basic and ClinicalAspects. New York, Alan R Liss, Inc, 1987, p 301-314. 10. 6riffith M J, Linker NJ, Ward D, et al: Adenosine in the diagnosis of broad complex tachycardia. Lancet1986;1:672-675. 11. Sharrna AD, Klein GJ, Yea R: Intravenous adenosine triphosphate during wide QRS complex tachycardia: Safety, therapeutic efficacy, and diagnostic efficacy. Am J Mad 1990;88:337-343. 12. Stewart BB, Bardy GH, Greene HL: Wide complex tachycardia: Misdiagnosis and outcome after emergent therapy. Ann Intern Mad 1986;104:766-771. 13. O'Taola KS, Holler MB, Menegazzi J J, et al: Intravenous veraparnil in the prehospital treatment of supraventricular tachycardia. Ann Emerfl Med 1990;19:291-294. 14. Grace R, Musto B, Arienzo V, et al: Treatment of paroxysmal supraventricular tachycardia in infancy with digitalis, adenosine-5'-triphosphate, and verapamil: A comparative study. Circulation 1982;66:504-508. 15. Clarke B, Rowland E, Barnes PJ, et al: Rapid and safe termination of supraventricular tachycardia in children with adenosine. Lancet1987;l:29g-301.
Address for reprints: Paul M Paris, MD, The Center for Emergency Medicine, 230 McKee Place, Pittsburgh, Pennsylvania 15213.
APRIL1992 21:4
ANNALS OF EMERGENCY MEDICINE
361/23
adenosine; paroxysmal supraveutricular tachycardia
Intravenous Adenosine in the Prehospital Treatmentof Paroxysmal SupraventricularTachycardia From the University of
James L McCabe, MD*
Pittsburgh Affiliated Residency
Gur C Adhar, MD ~
in Emergency Medicine;*
James J Menegazzi, PhD*
Electrophysiology Laboratory,
Paul M Paris, MD §
Study objective: To determine the clinical efficacy and safety of IV adenosine administration in the field for the treatment of paroxysmal supraventricular tachycardia (PSVT). Design: Prospective, consecutive case series.
The Mercy Hospital of Pittsburgh; t The Center for
Setting: An urban emergency medical services system.
Emergency Medicine of Western
P a r t i c i p a n t s : Thirty-seven adult patients in whom paramedics made
Pennsylvania; ¢ and Division of
the diagnosis of PSVT.
Emergency Medicine, University of Pittsburgh School of Medicine, § Pittsburgh, Pennsylvania. Received for publication May 14, 1991. Revision received July 1, 1991. Accepted for publication August 23, 1991. Presented at the Society for Academic Emergency Medicine Aunual Meeting in Washington, DC, May 1991. This study was funded in part by the Fujisawa Pharmaceutical Company and the Pittsburgh Emergency Medicine Foundation.
I n t e r v e n t i o n s : Six milligrams of adenosine was administered by
rapid IV bolus. If there was no effect within two minutes, a 12-mg bolus was given. This dose was repeated once if necessary. If there still was no effect, the medical command physician was contacted for further management. Measurements: Vital signs, symptoms, and a single-channel ECG were recorded before, during, and after the administration of adenosine. Results: On review of the ECG tracings, 26 patients (70%) were in PSVT. Eleven had rhythms other than PSVTon review, including five with atrial fibrillation, four with sinus tachycardia, and two with ventricular tachycardia. Of the 26 patients with PSVT,23 (88%) converted to sinus rhythm after adenosine administration. Eleven patients were hypotensive at presentation. Seven of these were in PSVTand became hemodynamically stable on conversion with adenosine. The four hypotensive patients with rhythms other than PSVT(two with atrial fibrillation and two with ventricular tachycardia) had no change in blood pressure after adenosine administration. Nine patients were subsequently found to have wide-complex tachycardia. None of these patients suffered hemodynamic compromise after adenosine administration, and side effects were infrequent, mild, and transient. Conclusion: Adenosine appears to be effective and safe for the prehospital treatment of PSVT. [McOabe JL, Adhar GC, Menegazzi J J, Paris PM: Intravenous adenosine in the prehospital treatment of paroxysmal supraventricular tachycardia. Ann EmergMedApri11992;21:358-361.]
20/358
ANNALS 0F EMERGENCYMEDICINE 21:4 APRIL1992
IV ADENOSINE McCabe et al
INTRODUCTION
MATERIALS AND METHODS
Paroxysmal supraventricular tachycardia (PSVT) is a commonly encountered dysrhythmia in the prehospital setting. Among the different types of PSVT, atrioventricular (AV) nodal re-entry and AV reciprocating tachycardia involving an accessory pathway account for the large majority and can be terminated by AV node blockade. 1 Current American H e a r t Association guidelines for the acute treatment of PSVT include vagal maneuvers and AV nodalblocking agents, such as digoxin, verapamil, and B-blockers, as well as synchronous electrical cardioversion in the unstable patient. 2 Theoretically, the prehospital treatment of PSVT should be the same; however, electrical cardioversion in this less-controlled setting should be used with caution. F u r t h e r m o r e , many emergency medical services (EMS) systems do not c a r r y verapamil. Adenosine is an endogenous nucleoside that produces transient AV nodal conduction delay after IV administration and thus is effective in terminating supraventricular tachycardias involving the AV node. 3 It has no direct effect on primary atrial dysrhythmias, including atrial fibrillation, atrial flutter, ectopic atrial tachycardia, and muhifocal atrial tachycardia. However, by slowing ventricular response, it can be useful in diagnosing these rhythms, a Other cardiac effects of adenosine include inhibition of sinus node automaticity and coronary artery vasodilatation. It is eliminated by active reuptake into cells and degradation by adenosine deaminase. Its half-life is approximately ten seconds. Because of such a short half-life, it is thought that adenosine exerts its effect during the first pass through the cardiac circulation and is most effective when given rapidly and close to the central circulation. Side effects are generally minor and include flushing, shortness of breath, chest pain, and lightheadedness. 3 Transient AV block, induced during the administration of adenosine, sometimes can be prolonged. P r e m a t u r e atrial, nodal, and ventricular beats are frequently seen during conversion but are rarely serious. All of these effects are transient and usually require no intervention. Adenosine does not significantly alter blood pressure, and to date there have been no reports of hemodynamic collapse associated with its use. Drug interactions include theophylline, which antagonizes its effects through receptor blockade, and dipyridamole, which enhances the effects of adenosine through inhibition of cellular reuptake. Although adenosine has been widely used in a controlled setting within the hospital, its use by paramedics in the prehospital setting has not been reported. The purpose of this investigation was to determine the clinical efficacy and safety of IV adenosine administration by paramedics in the field for the treatment of PSVT.
This investigation was a prospective, consecutive case series performed over a one-year period within the City of Pittsburgh EMS system. This is a single-tier system that operates 15 advanced life support units that receive on-line medical command from University of Pittsburgh emergency medicine residents and faculty. The annual call volume is approximately 60,000. Approval for the study was obtained from the HUman Rights Committee of the Western Pennsylvania Hospital and the State of Pennsylvania Department of Health, Division of Emergency Medical Services. Consecutive patients over the age of 18 years who were clinically diagnosed by paramedics as having PSVT were entered into the study. F o r the purpose of this study, PSVT was defined as a regular tachycardia at a rate between 150 and 250 beats p e r minute with a QRS duration of less than 120 ms. Patients were excluded if they had known hypersensitivity to adenosine or were in e x t r e m i s . After radio contact with a medical command physician, an IV line was placed in an antecubital vein, and 6 mg adenosine was administered as a r a p i d IV bolus; if there was no effect within two minutes, a 12-mg bolus was given. This dose was r e p e a t e d once if necessary. If there still was no response, no f u r t h e r adenosine was administered, and the medical command physician was recontacted to assist with f u r t h e r management. H e a r t rate, blood pressure, respirations, and symptoms were obtained before and after the administration of adenosine. Single-channel, continuous ECG tracings were obtained before, during, and after the administration of adenosine. The rhythm strips were subsequently reviewed by two of the investigators, one of whom was an electrophysiologist. In patients whose rhythms were not clearly determined by the prehospital rhythm strip, clinical information and 12-lead ECGs from the receiving hospital were used to assist in the diagnosis.
APRIL1992
21:4 ANNALS OF EMERGENCY MEDICINE
RESULTS Between March 1990 and April 1991, 37 consecutive p, ttients with a clinical diagnosis of PSVT received IV adenosin,~ in the field from paramedics. The mean age of patients in the study was 62 _+17 years; 20 were women. Fourteen patients (38%) had known structural heart disease. Based on subsequent review of ECG data, 26 of 37 patients (70%) met criteria for PSVT, five were in atrial fibrillation, four had sinus tachycardia, and two were in ventricular tachycardia. Twenty-three of the 26 patients in PSVT (88%) converted to sinus rhythm with adenosine. Of the three patients who did not convert, two were later found to have therapeutic levels of theophylline, and one received only a single 6-mg dose. The rhythm strips in the five patients in r a p i d atrial fibrillation initially a p p e a r e d regular; however, •
359/21
IV ADENOSINE M c C a b e et al
irregularity became a p p a r e n t as the ventricular response was transiently slowed with adenosine. Of the four patients in sinus tachycardia, three had no visible P waves on the prehospital strips but P waves were seen on subsequent 12lead ECGs. The fourth patient h a d first-degree AV block, and on review, P waves were seen b u r i e d within the p r i o r T wave. Adenosine caused transient sinus slowing in one of these patients and had no effect on the other three. Two patients were subsequently diagnosed as having VT. Adenosine had no effect on rhythm or blood pressure in either of these patients. At the receiving hospitals, one patient converted with lidocaine, and the other required electrical cardioversion. No adverse hemodynamic effects occurred in any patient receiving adenosine. Eleven patients were hypotensive (systolic blood pressure of 90 mm Hg or less) and had symptoms including chest pain, dyspnea, or lightheadedness on presentation. Seven of these with PSVT became hemodynamically stable after conversion to sinus r h y t h m with adenosine. The remaining four patients who were hypotensive and found to be in rhythms other than PSVT (including one patient with VT) exhibited no hemodynamic change with the administration of adenosine. On review, nine patients had a QRS duration of more than 120 ms and were diagnosed as having wide-complex tachycardia. Seven of these patients had pre-existing bundle b r a n c h blocks, two were in VT, and one r h y t h m was never clearly determined. None had hemodynamic deterioration with the administration of adenosine. Adverse effects occurred in six patients (16%), including two with flushing, two with chest pain, and one with dyspnea. One patient receiving dipyridamole at the time had a 3.6-second pause. All of these effects were transient and required no intervention. One patient (3%) had a recurrence of PSVT en route to the hospital.
DISCUSSION The results of this study demonstrate that adenosine is effective and safe in the prehospital treatment of PSVT. Although several rhythms were misinterpreted, adenosine was administered without harm. Presently, verapamil is the only pharmacologic treatment for PSVT a p p r o v e d for prehospital use. A recent multicenter, inpatient trial compared adenosine with verapamil in a prospective,
Figure. Termination of PSVT after adenosine
22/360
double-blind fashion and found the two to be equally effective in terminating PSVT. 5 Verapamil, however, has several characteristics that make it less desirable for use in the prehospital setting. It is a potent negative inotrope and vasodilator and can cause prolonged hypotension as well as precipitate acute congestive h e a r t failure. 6 Serious b r a d y d y s r h y t h m i a s and ventricular standstill can occur in patients on concomitant B-blocker therapy. Verapamil is known to have deleterious side effects in the setting of widecomplex tachycardia and can result in cardiac arrest if administered to a patient in VT. 6 It has also been shown to precipitate cardiac arrest when given to patients in atrial fibrillation with pre-excitation syndromes. 7 In contrast, adenosine does not cause any of these effects, and its extremely short half-life ensures p r o m p t resolution of any adverse effects. Adenosine has been given to patients in VT without adverse effect and has been shown to terminate catecholamine-induced VT. a'9 It also has been given to 14 patients with ventricular pre-excitation syndromes in atrial fibrillation without adverse effect. 10,11 There are two groups of patients in this study that deserve special mention. The first is the group of 11 patients who were hypotensive and symptomatic. The seven patients in PSVT were promptly converted to sinus rhythm with the administration of adenosine, which quickly restored hemodynamic stability. This precluded synchronous electrical cardioversion in these patients, which, although indicated in this situation, is much less desirable in the out-of-hospital setting, especially in the awake patient. This may have an impact on future advanced cardiac life support guidelines. The four hypotensive patients with rhythms other than PSVT f u r t h e r demonstrate adenosine's unique safety profile. The problems associated with the misdiagnosis and emergency treatment of wide-complex tachycardia have been well described. 12 Although our protocol was designed to include only narrow-complex tachycardia, a group of nine patients with a QRS duration of more than 120 ms were clinically diagnosed as having PSVT and were given adenosine. Two of them were in VT. Again, none of these patients developed any adverse hemodynamic effect. This experience is similar to that of two recently published investigations performed in electrophysiologic testing laboratories that have shown adenosine to be safe and effective in the diagnosis and treatment of wide-complex tachyeardia. 10,11 A previous prehospital investigation of PSVT in our system demonstrated a rhythm misidentification rate of 21%. 13 Since that time, paramedics have been required to r u n an ECG strip and use calipers to measure QRS regularity and duration. Despite this, the misidentification rate remains high, as demonstrated by our study, and further emphasizes the need for continuous ECG training as well as the limitation of single-channel ECG interpretation. •
ANNALS OF EMERGENCY MEDICINE 21:4 APRIL1992
IV ADENOSINE .~cCabe et al
CONCLUSION
REFERENCES
Adenosine is effective and safe for use by paramedics in the prehospital treatment of clinically diagnosed PSVT. It terminates PSVT in the majority of cases and is helpful in diagnosing other p r i m a r y atrial dysrhythmias. Based on a limited number of patients in this and other studies, l ° ' n adenosine appears to be safe in the setting of hypotension as well as wide-complex tachycardia. It may well preclude the prehospital use of verapamil for PSVT in the future and may also become an alternative to electrical cardioversion in the unstable patient who is not in e x t r e m i s . Future prehospital investigations could include a larger, muhicenter trial; a prospective evaluation of adenosine in patients with wide-complex t a c h y c a r d i a ; and use in the pediatric population. 14, is
1. Frame LN, Hoffman BF: Mechanisms of tachycardia, in Surawicz B (ed): Tachycardias. Boston, Martinus Nijhoff, 1984.
The authors thank the City of Pittsburgh p a r a m e d i c s , whose skill and cooperation made this study possible.
2. Standards and guidelines for cardiopulmonary resuscitation (CPR) and emergent cardiac care (ECC). JAMA 1986;255:2905. 3. DiMarco JP: Adenosine and supraventricular tachycardia, in Pelleg A, Michelson EL, Dreifus LS (ads): Cardiac Electrophysiology and Pharmacology of Adenosine and A TP: Basic and ClinicalAspects. New York, Alan R Liss, Inc, 1987, p 271-281. 4. BiMarco JP, Sellers TD, Lerman BB, et al: Diagnostic and therapeutic use of adenosine in patients with supraventricular tachyarrhythmias. JAm Coil Cardiol 1985;6:417-425. 5. DiMarco JP, Miles W, Akhtar M, et al: Adenosine for paroxysmal supraventricular tachycardia: Dose ranging and comparison to veraparnil. Ann Intern Med1990;113:104110. 6. Veraparnil for arrhythmias. MedLett1981;23:29-30. 7. McGovern B, Garan H, Ruskin JN: Precipitation of cardiac arrest by veraparnil in patients with Wolff-Parkinson-White syndrome. Ann Intern Med 1986;104:791-794. 8. Lerrnan BB, 8elardinelli L: Adenosine-sensitive ventricular tachycardia: Evidence suggesting cyclic AMP-mediated triggered activity. Circulation 1986;74:270-280. 9. Lerrnan BB, Be]ardinelli L: Effects of adenosine on ventricular tachycardia, in PeHeg A, Dreifus LS (eds): Cardiac Electrophysiology and Pharmacology of Adenosine and A TP: Basic and ClinicalAspects. New York, Alan R Liss, Inc, 1987, p 301-314. 10. 6riffith M J, Linker NJ, Ward D, et al: Adenosine in the diagnosis of broad complex tachycardia. Lancet1986;1:672-675. 11. Sharrna AD, Klein GJ, Yea R: Intravenous adenosine triphosphate during wide QRS complex tachycardia: Safety, therapeutic efficacy, and diagnostic efficacy. Am J Mad 1990;88:337-343. 12. Stewart BB, Bardy GH, Greene HL: Wide complex tachycardia: Misdiagnosis and outcome after emergent therapy. Ann Intern Mad 1986;104:766-771. 13. O'Taola KS, Holler MB, Menegazzi J J, et al: Intravenous veraparnil in the prehospital treatment of supraventricular tachycardia. Ann Emerfl Med 1990;19:291-294. 14. Grace R, Musto B, Arienzo V, et al: Treatment of paroxysmal supraventricular tachycardia in infancy with digitalis, adenosine-5'-triphosphate, and verapamil: A comparative study. Circulation 1982;66:504-508. 15. Clarke B, Rowland E, Barnes PJ, et al: Rapid and safe termination of supraventricular tachycardia in children with adenosine. Lancet1987;l:29g-301.
Address for reprints: Paul M Paris, MD, The Center for Emergency Medicine, 230 McKee Place, Pittsburgh, Pennsylvania 15213.
APRIL1992 21:4
ANNALS OF EMERGENCY MEDICINE
361/23
