Electrocardiographic Findings in a Young Man With Tachycardia and Hypotension—Discussion

doi:10.1001/archinte.172.15.1126

2012-08-13 00:00:00

Ecg interpretation Initial evaluation of the ECG showed sinus rhythm with regular PP intervals and QRS complexes of 2 different morphological appearances and amplitudes that occurred regularly in an alternating fashion, consistent with electrical alternans. However, closer inspection of these alternating QRS complexes revealed that one included a delta wave (Figure 2, arrows) and the other did not. This pattern is consistent with alternating conduction via an accessory pathway and the normal atrioventricular (AV) node His-Purkinje system; therefore, electrical alternans was not present. Clinical course Measurements of the patient's pulse and blood pressure revealed that they were not paradoxical. An emergency transthoracic echocardiogram demonstrated no pericardial effusion but did show severe biventricular systolic dysfunction, which was thought to be attributable to the patient's heavy methamphetamine use. The variation in the morphological appearance of the QRS complex was not persistent and did not reappear during his hospitalization. He underwent diuresis, with clinical improvement. Comment In this case, alternating QRS complexes with regular PP intervals, including the intermittent presence of delta waves (Figure 2), were evident. This pattern indicates intermittent ventricular preexcitation. Wolff-Parkinson-White syndrome (WPW), one of the forms of ventricular preexcitation, was identified in the ECG in this case by 4 criteria.1 First, the PR interval is approximately 130 ms for those QRS complexes that contain a delta wave and approximately 200 ms in those QRS complexes that do not contain a delta wave (best seen in lead V1). In WPW conduction, the PR interval is usually shorter than that observed during normal AV conduction because of ventricular preexcitation through the bundle of Kent (accessory pathway) as compared with the AV node. Second, the QRS duration is at the upper end of the normal range at 120 ms in the preexcited beats. Third, a delta wave is present. Most QRS complexes in WPW conduction are fusion complexes, in which the ventricles are depolarized from both the accessory pathway and the normal AV node His-Purkinje system. Depending on the degree of fusion, the PR intervals can vary from normal to extremely short, and the QRS complexes from near-normal in duration to maximally prolonged. The prominence of the delta waves will also vary from minimally discernible to unmistakenly prominent. View LargeDownload Figure 2. Intermittent preexcitation. Arrows indicate delta waves. In the ECG in this case, the delta wave and QRS complexes were negative in precordial leads V1 and V2 and positive in the left precordial leads, consistent with type B preexcitation and indicating a right-sided bundle of Kent. Finally, and also in accordance with type B preexcitation, repolarization abnormalities are observed in the left precordial leads: T-wave inversion and ST-segment depression are observed and follow only the preexcited beats, not those that are conducted normally through the AV node. Importantly, the alternating QRS complexes do not represent aberrant intraventricular conduction owing to premature atrial depolarizations occurring in a bigeminal fashion, because the PP intervals remain constant throughout. Intermittent preexcitation patterns, such as the one observed in this case, have been previously described in the setting of tachycardia, and block in the accessory pathway has been described during bradycardia.2-4 Previous reports have shown that patients with intermittent preexcitation at higher heart rates tend to have longer refractory periods of their accessory pathways and are therefore less likely to have tachyarrythmias involving accessory pathway conduction.3 Also, bradycardia-dependent block can exist in the accessory pathway, and it is thought that the refractory period of the accessory pathway is increased by a higher vagal tone or by spontaneous diastolic depolarization of automatic cardiocytes.4,5 At this patient's heart rate, the presence of a delta wave in alternating QRS complexes might indicate a 2:1 block in the accessory pathway. While the ECG in this case did not represent electrical alternans, such an ECG finding is of great importance in that it is a relatively specific finding for large pericardial effusion of any pathogenesis; cardiac tamponade may or may not be present and is not predicted by electrical alternans.6 True electrical alternans may occasionally be accompanied by P wave and QTU alternans in addition to QRS alternans.7 True electrical alternans should prompt early and aggressive investigation and correlation with the physical examination findings; imaging using echocardiography is required to confirm the diagnosis. Take-home points Electrical alternans can be mimicked by intermittent ventricular preexcitation due to WPW conduction. In electrical alternans, as opposed to intermittent ventricular preexcitation, the PR interval is constant between QRS complexes of differing amplitudes, and the only change in morphological appearance between the QRS complexes is their amplitude. Intermittent ventricular preexcitation can be triggered by both tachycardia and bradycardia depending on the refractory period of the accessory pathway. Electrical alternans is specific for large pericardial effusions, but the absence of this finding on ECG does not rule out large pericardial effusion or tamponade. Return to Question Back to top Article Information Correspondence: Victoria N. Parikh, MD, Department of Internal Medicine, University of California, San Francisco, 1545 Divisadero Ave, Mailbox DGIM, Second Floor, San Francisco, CA 94115 (victoria.parikh@ucsf.edu). Published Online: July 16, 2012. doi:10.1001/archinternmed.2012.2727 Financial Disclosure: None reported. References 1. Chou T-C. Electrocardiography in Clinical Practice: Adult and Pediatric. 4th ed. Philadelphia, PA: WB Saunders Co; 1996 2. Kinoshita S, Katoh T, Hagisawa K, Kimura K. Accessory-pathway block on alternate beats in the Wolff-Parkinson-White syndrome: supernormal conduction as the mechanism. J Electrocardiol. 2007;40(5):442-44717276453PubMedGoogle ScholarCrossref 3. Klein GJ, Gulamhusein SS. Intermittent preexcitation in the Wolff-Parkinson-White syndrome. Am J Cardiol. 1983;52(3):292-2966869275PubMedGoogle ScholarCrossref 4. Ortega-Carnicer J, Benezet-Peñaranda J. Bradycardia-dependent block in the accessory pathway in a patient with alternans Wolff-Parkinson-White syndrome. J Electrocardiol. 2006;39(4):419-42016697399PubMedGoogle ScholarCrossref 5. Kinoshita S, Katoh T. Apparent bradycardia-dependent block in the accessory pathway in intermittent Wolff-Parkinson-White syndrome. J Electrocardiol. 1998;31(2):151-1539588662PubMedGoogle ScholarCrossref 6. Guberman BA, Fowler NO, Engel PJ, Gueron M, Allen JM. Cardiac tamponade in medical patients. Circulation. 1981;64(3):633-6406455217PubMedGoogle ScholarCrossref 7. Littmann D, Spodick DH. Total electrical alternation in pericardial disease. Circulation. 1958;17(5):912-91713537279PubMedGoogle ScholarCrossref

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$Ecg interpretation Initial evaluation of the ECG showed sinus rhythm with regular PP intervals and QRS complexes of 2 different morphological appearances and amplitudes that occurred regularly in an alternating fashion, consistent with electrical alternans. However, closer inspection of these alternating QRS complexes revealed that one included a delta wave (Figure 2, arrows) and the other did not. This pattern is consistent with alternating conduction via an accessory pathway and the normal atrioventricular (AV) node His-Purkinje system; therefore, electrical alternans was not present. Clinical course Measurements of the patient's pulse and blood pressure revealed that they were not paradoxical. An emergency transthoracic echocardiogram demonstrated no pericardial effusion but did show severe biventricular systolic dysfunction, which was thought to be attributable to the patient's heavy methamphetamine use. The variation in the morphological appearance of the QRS complex was not persistent and did not reappear during his hospitalization. He underwent diuresis, with clinical improvement. Comment In this case, alternating QRS complexes with regular PP intervals, including the intermittent presence of delta waves (Figure 2), were evident. This pattern indicates intermittent ventricular preexcitation. Wolff-Parkinson-White syndrome (WPW), one of the forms of ventricular preexcitation, was identified in the ECG in this case by 4 criteria.1 First, the PR interval is approximately 130 ms for those QRS complexes that contain a delta wave and approximately 200 ms in those QRS complexes that do not contain a delta wave (best seen in lead V1). In WPW conduction, the PR interval is usually shorter than that observed during normal AV conduction because of ventricular preexcitation through the bundle of Kent (accessory pathway) as compared with the AV node. Second, the QRS duration is at the upper end of the normal range at 120 ms in the preexcited beats. Third, a delta wave is present. Most QRS complexes in WPW conduction are fusion complexes, in which the ventricles are depolarized from both the accessory pathway and the normal AV node His-Purkinje system. Depending on the degree of fusion, the PR intervals can vary from normal to extremely short, and the QRS complexes from near-normal in duration to maximally prolonged. The prominence of the delta waves will also vary from minimally discernible to unmistakenly prominent. View LargeDownload Figure 2. Intermittent preexcitation. Arrows indicate delta waves. In the ECG in this case, the delta wave and QRS complexes were negative in precordial leads V1 and V2 and positive in the left precordial leads, consistent with type B preexcitation and indicating a right-sided bundle of Kent. Finally, and also in accordance with type B preexcitation, repolarization abnormalities are observed in the left precordial leads: T-wave inversion and ST-segment depression are observed and follow only the preexcited beats, not those that are conducted normally through the AV node. Importantly, the alternating QRS complexes do not represent aberrant intraventricular conduction owing to premature atrial depolarizations occurring in a bigeminal fashion, because the PP intervals remain constant throughout. Intermittent preexcitation patterns, such as the one observed in this case, have been previously described in the setting of tachycardia, and block in the accessory pathway has been described during bradycardia.2-4 Previous reports have shown that patients with intermittent preexcitation at higher heart rates tend to have longer refractory periods of their accessory pathways and are therefore less likely to have tachyarrythmias involving accessory pathway conduction.3 Also, bradycardia-dependent block can exist in the accessory pathway, and it is thought that the refractory period of the accessory pathway is increased by a higher vagal tone or by spontaneous diastolic depolarization of automatic cardiocytes.4,5 At this patient's heart rate, the presence of a delta wave in alternating QRS complexes might indicate a 2:1 block in the accessory pathway. While the ECG in this case did not represent electrical alternans, such an ECG finding is of great importance in that it is a relatively specific finding for large pericardial effusion of any pathogenesis; cardiac tamponade may or may not be present and is not predicted by electrical alternans.6 True electrical alternans may occasionally be accompanied by P wave and QTU alternans in addition to QRS alternans.7 True electrical alternans should prompt early and aggressive investigation and correlation with the physical examination findings; imaging using echocardiography is required to confirm the diagnosis. Take-home points Electrical alternans can be mimicked by intermittent ventricular preexcitation due to WPW conduction. In electrical alternans, as opposed to intermittent ventricular preexcitation, the PR interval is constant between QRS complexes of differing amplitudes, and the only change in morphological appearance between the QRS complexes is their amplitude. Intermittent ventricular preexcitation can be triggered by both tachycardia and bradycardia depending on the refractory period of the accessory pathway. Electrical alternans is specific for large pericardial effusions, but the absence of this finding on ECG does not rule out large pericardial effusion or tamponade. Return to Question Back to top Article Information Correspondence: Victoria N. Parikh, MD, Department of Internal Medicine, University of California, San Francisco, 1545 Divisadero Ave, Mailbox DGIM, Second Floor, San Francisco, CA 94115 (victoria.parikh@ucsf.edu). Published Online: July 16, 2012. doi:10.1001/archinternmed.2012.2727 Financial Disclosure: None reported. References 1. Chou T-C. Electrocardiography in Clinical Practice: Adult and Pediatric. 4th ed. Philadelphia, PA: WB Saunders Co; 1996 2. Kinoshita S, Katoh T, Hagisawa K, Kimura K. Accessory-pathway block on alternate beats in the Wolff-Parkinson-White syndrome: supernormal conduction as the mechanism. J Electrocardiol. 2007;40(5):442-44717276453PubMedGoogle ScholarCrossref 3. Klein GJ, Gulamhusein SS. Intermittent preexcitation in the Wolff-Parkinson-White syndrome. Am J Cardiol. 1983;52(3):292-2966869275PubMedGoogle ScholarCrossref 4. Ortega-Carnicer J, Benezet-Peñaranda J. Bradycardia-dependent block in the accessory pathway in a patient with alternans Wolff-Parkinson-White syndrome. J Electrocardiol. 2006;39(4):419-42016697399PubMedGoogle ScholarCrossref 5. Kinoshita S, Katoh T. Apparent bradycardia-dependent block in the accessory pathway in intermittent Wolff-Parkinson-White syndrome. J Electrocardiol. 1998;31(2):151-1539588662PubMedGoogle ScholarCrossref 6. Guberman BA, Fowler NO, Engel PJ, Gueron M, Allen JM. Cardiac tamponade in medical patients. Circulation. 1981;64(3):633-6406455217PubMedGoogle ScholarCrossref 7. Littmann D, Spodick DH. Total electrical alternation in pericardial disease. Circulation. 1958;17(5):912-91713537279PubMedGoogle ScholarCrossref$

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Electrocardiographic Findings in a Young Man With Tachycardia and Hypotension—Discussion

Electrocardiographic Findings in a Young Man With Tachycardia and Hypotension—Discussion

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Electrocardiographic Findings in a Young Man With Tachycardia and Hypotension—Discussion

Electrocardiographic Findings in a Young Man With Tachycardia and Hypotension—Discussion

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