s), Futura Publishing, Mount Kisco 1990. p.341. 31. Kastor JA, Yurchak PM. Recognition of digitalis intoxication in the presence of atrial fibrillation. Ann Intern Med 1967; 67:1045. 32. Carleton RA, Miller PH, Graettinger JS. Effects of ouabain, atropine, and ouabain and atropine on A-V nodal conduction in man. Circ Res 1967; 20:283. 33. Toda N, West TC. The action of ouabain on the function of the atrioventricular node in rabbits. J Pharmacol Exp Ther 1969; 169:287. 34. Goodman DJ, Rossen RM, Cannom DS, et al. Effect of digoxin on atioventricular conduction. Studies in patients with and without cardiac autonomic innervation. Circulation 1975; 51:251. https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 12/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate 35. Ricci DR, Orlick AE, Reitz BA, et al. Depressant effect of digoxin on atrioventricular conduction in man. Circulation 1978; 57:898. 36. Childers R. Classification of cardiac dysrhythmias. Med Clin North Am 1976; 60:3. 37. Fisch C, Knoebel SB. Digitalis cardiotoxicity. J Am Coll Cardiol 1985; 5:91A. 38. Kleiger R, Lown B. Cardioversion and digitalis. II. Clinical studies. Circulation 1966; 33:878. 39. Morris SN, Zipes DP. His bundle electrocardiography during bidirectional tachycardia. Circulation 1973; 48:32. 40. Priori SG, Napolitano C, Memmi M, et al. Clinical and molecular characterization of patients with catecholaminergic polymorphic ventricular tachycardia. Circulation 2002; 106:69. Topic 944 Version 29.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 13/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate GRAPHICS Single-lead electrocardiogram (ECG) showing lead V1 in type I (Wenckebach type) sinoatrial block There is a 3:2 SA block, resulting in group beating of pairs of sinus beats. The P-P interval during the pause has a duration (1040 msec) that is less than two P-P cycles (1360 msec); this finding distinguishes this arrhythmia from type II SA block in which the pause duration is the same as that of two P-P cycles. Courtesy of Morton Arnsdorf, MD. Graphic 68081 Version 3.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 14/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing lead V5 in type II sinoatrial block There is a 3:2 SA block, resulting in group beating of pairs of sinus beats. The P-P interval during the pause has a duration (1840 msec) that is approximately equal to two P-P cycles (920 msec); this finding distinguishes this arrhythmia from type I SA block in which the pause duration is less than that of two P-P cycles. There may be some sinus variability, as in this case, due to sinus arrhythmia and possibly to baroreceptor responses to varying diastolic filling intervals. Courtesy of Morton Arnsdorf, MD. Graphic 54936 Version 3.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 15/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing atrial tachycardia with 2:1 atrioventricular (AV) block Atrial tachycardia with 2:1 atrioventricular (AV) block. The atrial rate is about 160 beats/min while the ventricular rate is about 80 beats/min. The nonconducted P waves (arrows) are superimposed on the ST-T segments. The P waves have a similar morphology to normal P waves suggesting that the ectopic site is near or even in the sinoatrial node. This arrhythmia may be an important sign of digoxin toxicity, but can also occur in other settings. Courtesy of Ary Goldberger, MD. Graphic 56994 Version 4.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 16/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing atrial fibrillation (AF) with junctional escape beats suggesting digoxin toxicity The 4 electrocardiograms in this sequence demonstrate increasing severity of digoxin toxicity in a patient with atrial fibrillation. This ECG shows atrial fibrillation with an irregularly irregular ventricular response. However, the longest recurring R-R intervals are constant, suggesting junctional escape beats due to AV nodal block. The escape interval of 680 msec indicates an accelerated automatic pacemaker with a rate of 88 beats/min. The four electrocardiograms are adapted from: Childers R, Med Clin North Am 1976; 60:3. Graphic 64396 Version 5.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 17/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing atrial fibrillation with an accelerated junctional pacemaker The 4 electrocardiograms in this sequence demonstrate increasing severity of digoxin toxicity in a patient with atrial fibrillation. In this strip, the R-R intervals are constant, as the ventricles are controlled by an accelerated junctional pacemaker, resulting in a regular tachycardia at 115 beats per minute. Physical examination at this time might lead to the erroneous diagnosis of a regular sinus mechanism. The four electrocardiograms are adapted from: Childers R, Med Clin North Am 1976; 60:3. Graphic 76154 Version 6.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 18/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing atrial fibrillation with further accelerated junctional pacemaker The 4 electrocardiograms in this sequence demonstrate increasing severity of digoxin toxicity in a patient with atrial fibrillation. In this strip, the R-R intervals remain constant with further acceleration of the junctional pacemaker to a rate of 142 beats per minute. The four electrocardiograms are adapted from: Childers R, Med Clin North Am 1976; 60:3. Graphic 55119 Version 7.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 19/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing atrial fibrillation and a junctional pacemaker with a 4:3 Wenckebach exit block The 4 electrocardiograms in this sequence demonstrate increasing severity of digoxin toxicity in a patient with atrial fibrillation. In this strip, the result is group beating characterized by three beats with decreasing R-R intervals. On physical examination, this seemingly irregular rhythm might lead to the mistaken diagnosis of an irregularly irregular response to atrial fibrillation, rather than arrhythmia associated with severe digoxin toxicity. This patient presented with this ECG; the preceding electrocardiograms reflected (in reverse order) the sequence of recovery as the effect of digoxin wore off. The four electrocardiograms are adapted from: Childers R, Med Clin North Am 1976; 60:3. Graphic 66940 Version 7.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 20/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing first degree atrioventricular (AV) block I Electrocardiogram of lead II showing normal sinus rhythm, first degree atrioventricular block with a prolonged PR interval of 0.30 seconds, and a QRS complex of normal duration. The tall P waves and P wave duration of approximately 0.12 seconds suggest concurrent right atrial enlargement. Courtesy of Morton Arnsdorf, MD. Graphic 67882 Version 5.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 21/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Electrocardiogram showing Mobitz type I (Wenckebach) atrioventricular block Single-lead electrocardiogram showing Mobitz type I (Wenckebach) second-degree atrioventricular block with 5:4 conduction. The characteristics of this arrhythmia include: a progressively increasing PR interval until a P wave is not conducted (arrow), a progressive decrease in the increment in the PR interval, a progressive decrease in the RR interval, and the RR interval that includes the dropped beat (0.96 sec) is less than twice the RR interval between conducted beats (0.53 to 0.57 sec). Courtesy of Morton Arnsdorf, MD. Graphic 73051 Version 6.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 22/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing sinus rhythm with third degree (complete) AV block Sinus rhythm with third degree (complete) heart block. There is independent atrial (as shown by the P waves) and ventricular activity, with respective rates of 83 and 43 beats per minute. The wide QRS complexes may represent a junctional escape rhythm with underlying bundle branch block or an idioventricular pacemaker. Courtesy of Ary Goldberger, MD. Graphic 72863 Version 6.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 23/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing bidirectional ventricular tachycardia (VT) Rhythm strip showing bidirectional ventricular tachycardia (VT) which may be a manifestation of digoxin toxicity. This rare, life-threatening tachyarrhythmia is characterized by beat-to-beat changes in the polarity of consecutive premature ventricular complexes. Courtesy of Ary Goldberger, MD. Graphic 71796 Version 3.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 24/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Single-lead electrocardiogram (ECG) showing sinus rhythm with ventricular bigeminy Sinus rhythm with ventricular bigeminy. Each sinus beat is followed by a uniform premature complex with prolonged duration and no apparent P wave; these findings are indicative of ventricular ectopic beats. Courtesy of Ary Goldberger, MD. Graphic 72547 Version 4.0 Normal rhythm strip Normal rhythm strip in lead II. The PR interval is 0.15 sec and the QRS duration is 0.08 sec. Both the P and T waves are upright. Courtesy of Morton F Arnsdorf, MD. Graphic 59022 Version 3.0 https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 25/26 7/5/23, 11:14 AM Cardiac arrhythmias due to digoxin toxicity - UpToDate Contributor Disclosures Ary L Goldberger, MD Other Financial Interest: Elsevier book royalties [Clinical electrocardiography]. All of the relevant financial relationships listed have been mitigated. Evan Schwarz, MD No relevant financial relationship(s) with ineligible companies to disclose. Nisha Parikh, MD, MPH No relevant financial relationship(s) with ineligible companies to disclose. Contributor disclosures are reviewed for conflicts of interest by the editorial group. When found, these are addressed by vetting through a multi-level review process, and through requirements for references to be provided to support the content. Appropriately referenced content is required of all authors and must conform to UpToDate standards of evidence. Conflict of interest policy https://www.uptodate.com/contents/cardiac-arrhythmias-due-to-digoxin-toxicity/print 26/26