ECG Puzzler A regular feature of the American Journal of Critical Care, the ECG Puzzler addresses electrocardiogram (ECG) interpretation for clinical practice. To send an eLetter or to contribute to an online discussion about this article, visit www.ajcconline.org and click “Respond to This Article” on either the full-text or PDF view of the article. We welcome letters regarding this feature.
ASYMPTOMATIC IRREGULAR CARDIAC RHYTHM By Mary G. Carey, RN, PhD, CNS, Salah S. Al-Zaiti, RN, PhD, NP, Teri M. Kozik, RN, PhD, CNS, CCRN, M. Pelter, RN, PhD
and Michele
Scenario: This is a rhythm strip of lead V5 from a 24-hour Holter study of a patient who is scheduled for elective orthopedic surgery. He is a physically fit 24-year-
old white male with no medical history. The Holter study was performed because during his preoperative evaluation he was noted to have an irregular pulse rate.
v5
v5
v5
Interpretation Questions: 1. Is the ECG properly calibrated (10 mm) and are leads properly placed? If no, interpret cautiously. 2. Is this a sinus rhythm (one P wave preceding every QRS complex)? If no, check for number of P waves in relation to QRS complexes. 3. Is the heart rate (R-R interval) normal (60-100 beats/min)? If no, check for supra-ventricular or ventricular arrhythmias. 4. Is the QRS complex narrow (duration < 110 milliseconds [ms] in V1)? If no, check for bundle branch blocks (BBBs), pacing, or ventricular arrhythmia. 5. Is the ST segment deviated (> 2 mm in V2-V3, or > 1 mm in other leads)? If yes, check for similar deviations in contiguous cardiac territories. 6. Is the T wave inverted in relation to the QRS (> 0.5 mV)? If yes, check for ST deviation or conduction abnormalities. 7. Is the QT interval lengthened (> 450 ms [women] or > 470 ms [men])? If yes, check for ventricular arrhythmias or left ventricular hypertrophy. 8. Is R- or S-wave amplitude enlarged (S wave V1 + R wave V5 > 35 mm)? If yes, check for axis deviation or other chamber hypertrophy criteria.
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
Mary G. Carey is associate director for clinical nursing research, Strong Memorial Hospital, Rochester, New York. Salah S. Al-Zaiti is an assistant professor at the Acute and Tertiary Care Department, University of Pittsburgh, Pennsylvania. New York. Teri M. Kozik is a nurse researcher at St. Joseph’s Medical Center, Stockton, California. Michele M. Pelter is a professor at the Orvis School of Nursing, University of Nevada, Reno. ©2014 American Association of Critical-Care Nurses, doi: http://dx.doi.org/10.4037/ajcc2014438
www.ajcconline.org
AJCC AMERICAN JOURNAL OF CRITICAL CARE, September 2014, Volume 23, No. 5 Downloaded from ajcc.aacnjournals.org at YALE MEDICAL LIBRARY on July 14, 2015
429
v5
P-P = 600 msec
P-P = 1100
Inhalation
Exhalation
v5
v5
Answers: 1. Unable to determine in the absence of a calibration mark. 2. Yes, there is a P wave before every QRS complex and the P-R interval is constant. However, the P-P interval is irregular. 3. The heart rate is within the normal rate but the rhythm is irregular. 4. Yes, the QRS complex is narrow. 5. The ST segments are not deviated. 6. The T waves are not inverted. 7. The QT interval is not prolonged. 8. Left ventricular hypertrophy cannot be assessed because lead V1 is not present.
430
Interpretation and Rationale
Mechanism and Management
This rhythm is an example of marked respiratory sinus arrhythmia at 71 beats/min. In this rhythm, sinus rhythm is present along with beat to beat variations in the P-P interval (time measured between consecutive P waves). This produces an irregular R-R interval resulting in sinus arrhythmia. It is extremely noticeable so the word marked is added to the description. Sinus arrhythmia is a change in heart rate that is concurrent with the respiratory cycle, so that with inhalation the heart rate accelerates and with exhalation the heart rate decelerates. The characteristics of respiratory sinus arrhythmia include: • The P-wave morphology is consistent. • The PR interval is fixed. • Variation of the P-P interval is greater than 120 milliseconds (example above demonstrates a difference of nearly 200 msec), • The P-P interval gradually lengthens and shortens in a sustained pattern, usually related to the respiratory cycle.
The Bainbridge reflex may explain sinus arrhythmia that occurs when venous return to the right atrium is increased during inhalation. This results in heart rate acceleration and increased force of contraction in response to venoatrial stretch receptor activation. These compensatory mechanisms lead to an increase in the cardiac output. This reflex opposes the carotid baroreceptor to increase the heart rate when myocardial stretch is decreased (eg, hypotension, hypovolemia). Respiratory sinus arrhythmia is considered a normal finding in children and young adults, and usually disappears with age. The decrease in the incidence with age is thought to occur due to decreases in carotid artery elasticity and baroreceptor reflex sensitivity. In this patient, no intervention is necessary. The findings of the Holter study should be communicated to the surgical team so that this benign arrhythmia does not interfere with this patient’s pre- and postoperative care.
AJCC AMERICAN JOURNAL OF CRITICAL CARE, September 2014, Volume 23, No. 5 Downloaded from ajcc.aacnjournals.org at YALE MEDICAL LIBRARY on July 14, 2015
www.ajcconline.org
Asymptomatic Irregular Cardiac Rhythm Mary G. Carey, Salah S. Al-Zaiti, Teri M. Kozik and Michele M. Pelter Am J Crit Care 2014;23:429-430 doi: 10.4037/ajcc2014438 © 2014 American Association of Critical-Care Nurses Published online http://www.ajcconline.org Personal use only. For copyright permission information: http://ajcc.aacnjournals.org/cgi/external_ref?link_type=PERMISSIONDIRECT
Subscription Information http://ajcc.aacnjournals.org/subscriptions/ Information for authors http://ajcc.aacnjournals.org/misc/ifora.xhtml Submit a manuscript http://www.editorialmanager.com/ajcc Email alerts http://ajcc.aacnjournals.org/subscriptions/etoc.xhtml
AJCC, the American Journal of Critical Care, is the official peer-reviewed research journal of the American Association of Critical-Care Nurses (AACN), published bimonthly by The InnoVision Group, 101 Columbia, Aliso Viejo, CA 92656. Telephone: (800) 899-1712, (949) 362-2050, ext. 532. Fax: (949) 362-2049. Copyright © 2014 by AACN. All rights reserved.
Downloaded from ajcc.aacnjournals.org at YALE MEDICAL LIBRARY on July 14, 2015
ASYMPTOMATIC IRREGULAR CARDIAC RHYTHM By Mary G. Carey, RN, PhD, CNS, Salah S. Al-Zaiti, RN, PhD, NP, Teri M. Kozik, RN, PhD, CNS, CCRN, M. Pelter, RN, PhD
and Michele
Scenario: This is a rhythm strip of lead V5 from a 24-hour Holter study of a patient who is scheduled for elective orthopedic surgery. He is a physically fit 24-year-
old white male with no medical history. The Holter study was performed because during his preoperative evaluation he was noted to have an irregular pulse rate.
v5
v5
v5
Interpretation Questions: 1. Is the ECG properly calibrated (10 mm) and are leads properly placed? If no, interpret cautiously. 2. Is this a sinus rhythm (one P wave preceding every QRS complex)? If no, check for number of P waves in relation to QRS complexes. 3. Is the heart rate (R-R interval) normal (60-100 beats/min)? If no, check for supra-ventricular or ventricular arrhythmias. 4. Is the QRS complex narrow (duration < 110 milliseconds [ms] in V1)? If no, check for bundle branch blocks (BBBs), pacing, or ventricular arrhythmia. 5. Is the ST segment deviated (> 2 mm in V2-V3, or > 1 mm in other leads)? If yes, check for similar deviations in contiguous cardiac territories. 6. Is the T wave inverted in relation to the QRS (> 0.5 mV)? If yes, check for ST deviation or conduction abnormalities. 7. Is the QT interval lengthened (> 450 ms [women] or > 470 ms [men])? If yes, check for ventricular arrhythmias or left ventricular hypertrophy. 8. Is R- or S-wave amplitude enlarged (S wave V1 + R wave V5 > 35 mm)? If yes, check for axis deviation or other chamber hypertrophy criteria.
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
❑ Yes
❑ No
❑ NA
Mary G. Carey is associate director for clinical nursing research, Strong Memorial Hospital, Rochester, New York. Salah S. Al-Zaiti is an assistant professor at the Acute and Tertiary Care Department, University of Pittsburgh, Pennsylvania. New York. Teri M. Kozik is a nurse researcher at St. Joseph’s Medical Center, Stockton, California. Michele M. Pelter is a professor at the Orvis School of Nursing, University of Nevada, Reno. ©2014 American Association of Critical-Care Nurses, doi: http://dx.doi.org/10.4037/ajcc2014438
www.ajcconline.org
AJCC AMERICAN JOURNAL OF CRITICAL CARE, September 2014, Volume 23, No. 5 Downloaded from ajcc.aacnjournals.org at YALE MEDICAL LIBRARY on July 14, 2015
429
v5
P-P = 600 msec
P-P = 1100
Inhalation
Exhalation
v5
v5
Answers: 1. Unable to determine in the absence of a calibration mark. 2. Yes, there is a P wave before every QRS complex and the P-R interval is constant. However, the P-P interval is irregular. 3. The heart rate is within the normal rate but the rhythm is irregular. 4. Yes, the QRS complex is narrow. 5. The ST segments are not deviated. 6. The T waves are not inverted. 7. The QT interval is not prolonged. 8. Left ventricular hypertrophy cannot be assessed because lead V1 is not present.
430
Interpretation and Rationale
Mechanism and Management
This rhythm is an example of marked respiratory sinus arrhythmia at 71 beats/min. In this rhythm, sinus rhythm is present along with beat to beat variations in the P-P interval (time measured between consecutive P waves). This produces an irregular R-R interval resulting in sinus arrhythmia. It is extremely noticeable so the word marked is added to the description. Sinus arrhythmia is a change in heart rate that is concurrent with the respiratory cycle, so that with inhalation the heart rate accelerates and with exhalation the heart rate decelerates. The characteristics of respiratory sinus arrhythmia include: • The P-wave morphology is consistent. • The PR interval is fixed. • Variation of the P-P interval is greater than 120 milliseconds (example above demonstrates a difference of nearly 200 msec), • The P-P interval gradually lengthens and shortens in a sustained pattern, usually related to the respiratory cycle.
The Bainbridge reflex may explain sinus arrhythmia that occurs when venous return to the right atrium is increased during inhalation. This results in heart rate acceleration and increased force of contraction in response to venoatrial stretch receptor activation. These compensatory mechanisms lead to an increase in the cardiac output. This reflex opposes the carotid baroreceptor to increase the heart rate when myocardial stretch is decreased (eg, hypotension, hypovolemia). Respiratory sinus arrhythmia is considered a normal finding in children and young adults, and usually disappears with age. The decrease in the incidence with age is thought to occur due to decreases in carotid artery elasticity and baroreceptor reflex sensitivity. In this patient, no intervention is necessary. The findings of the Holter study should be communicated to the surgical team so that this benign arrhythmia does not interfere with this patient’s pre- and postoperative care.
AJCC AMERICAN JOURNAL OF CRITICAL CARE, September 2014, Volume 23, No. 5 Downloaded from ajcc.aacnjournals.org at YALE MEDICAL LIBRARY on July 14, 2015
www.ajcconline.org
Asymptomatic Irregular Cardiac Rhythm Mary G. Carey, Salah S. Al-Zaiti, Teri M. Kozik and Michele M. Pelter Am J Crit Care 2014;23:429-430 doi: 10.4037/ajcc2014438 © 2014 American Association of Critical-Care Nurses Published online http://www.ajcconline.org Personal use only. For copyright permission information: http://ajcc.aacnjournals.org/cgi/external_ref?link_type=PERMISSIONDIRECT
Subscription Information http://ajcc.aacnjournals.org/subscriptions/ Information for authors http://ajcc.aacnjournals.org/misc/ifora.xhtml Submit a manuscript http://www.editorialmanager.com/ajcc Email alerts http://ajcc.aacnjournals.org/subscriptions/etoc.xhtml
AJCC, the American Journal of Critical Care, is the official peer-reviewed research journal of the American Association of Critical-Care Nurses (AACN), published bimonthly by The InnoVision Group, 101 Columbia, Aliso Viejo, CA 92656. Telephone: (800) 899-1712, (949) 362-2050, ext. 532. Fax: (949) 362-2049. Copyright © 2014 by AACN. All rights reserved.
Downloaded from ajcc.aacnjournals.org at YALE MEDICAL LIBRARY on July 14, 2015
