Multiform accelerated idioventricular rhythm in acute myocardial infarction: electrocardiographic characteristics and response to verapamil

Accelerated idioventricular rhythm in the post-thrombolytic era: incidence, prognostic implications, and modulating mechanisms after direct percutaneous coronary intervention

BACKGROUND

In the thrombolytic era, the occurrence of accelerated idioventricular rhythm (AIR) has been proposed to be a specific marker for successful reperfusion. The incidence, prognostic implications, and potential modulating mechanisms of AIR after successful restoration of antegrade flow by means of modern reperfusion therapy (i.e., direct percutaneous coronary intervention (PCI)) has thus far not been investigated.

METHODS

We prospectively investigated 125 consecutive patients undergoing direct PCI for a first acute myocardial infarction (AMI). The incidence of AIR was determined from 24-hour Holter monitoring, initiated prior to PCI.

RESULTS

AIR appeared in 19 patients (15.2%). There were no significant differences between patients with or without AIR regarding baseline clinical characteristics. The incidence of AIR was not different between patients with TIMI 2 and 3 flow (13% vs 16%). There were no differences in the incidence of major cardiac events within 12-month follow-up in patients with and without AIR. Patients with AIR exhibited higher mean R-R intervals (mean 24-hour R-R interval: 871.3 +/- 121 vs 796.4 +/- 100 ms, P < 0.01), higher hourly mean values of heart rate variability (SDNN, 64.7 +/- 26 vs 49.4 +/- 20 ms, P < 0.01; rMSSD, 29.3 +/- 15 vs 22.0 +/- 12 ms, P < 0.01) and lower serum norepinephrine concentrations (60 minute after PCI, 478.9 +/- 357 vs 649.0 +/- 499 pg/ml, P < 0.05).

CONCLUSIONS

Our findings indicate that AIR is an nonspecific marker for reperfusion of the infarct-related artery in AMI and thus, predate previous observations of the thrombolytic era. Even though, AIR was associated with higher tonic vagal tone and lower sympathetic activity, the occurrence of AIR had no prognostic impact on the clinical course and was not able to discriminate between complete and incomplete reperfusion.

Triggered activity due to delayed afterdepolarizations in sites of focal origin of ischemic ventricular tachycardia

This study for the first time systematically evaluated the site of origin of focal ventricular tachycardia (VT) induced 1–3 h after acute coronary artery ligation in dogs. We determined whether delayed afterdepolarizations (DADs) and triggered activity (TA) are more often recorded from ischemic endocardium excised from focal sites of VT origin. A total of 145 α-chloralose-anesthetized dogs were studied: in 54 dogs without inducible VT, normal or ischemic endocardium was investigated in vitro; in 91 dogs, inducible VT was studied by three-dimensional activation mapping, with in vitro study of 51 endocardial foci compared with 40 endocardial ischemic sites not of VT origin. Incidence of DADs (71% vs. 33%, P < 0.05) and TA (32% vs. 11%, P < 0.05) was greater in ischemic than in normal Purkinje tissues. Purkinje sites of origin of focal VT demonstrated the greatest frequency of DADs (92%, P < 0.05) and TA (75%, P < 0.05), with repetitive TA predominating. Similar results were obtained in endocardial sites of origin. Action potentials were mildly depolarized and prolonged in the focal sites of origin. These abnormalities were stable up to 2.5 h of recording. This study demonstrated that DADs and TA may underlie a majority of focal VTs in ischemic endocardium and Purkinje tissue.

[Incessant ventricular tachycardia as a manifestation of myocardial ischemia]

We describe four patients with incessant ventricular tachycardia after the acute phase of a myocardial infarction. Two of them had a slow heart rate, and myocardial revascularization resolved the arrhythmia after ischemia was demonstrated. In the other two cases, very fast tachycardias were interrupted by means of intravenous verapamil and clinical stabilization was achieved after failure of amiodarone and lidocaine. In one of them, revascularization prevented new recurrences, but it was not feasible in the second patient, who developed new arrhythmias. The possible mechanisms of these tachycardias and their clinical and therapeutic implications are discussed.

Antiarrhythmic efficacy of dipyridamole in treatment of reperfusion arrhythmias : evidence for cAMP-mediated triggered activity as a mechanism responsible for reperfusion arrhythmias

BACKGROUND

Intracellular calcium overload is believed to play an important role in development of reperfusion arrhythmias. Dipyridamole, an inhibitor of cellular uptake of adenosine, may prevent or terminate reperfusion arrhythmias by reducing intracellular calcium overload.

METHODS AND RESULTS

First, we tested for a preventive effect of dipyridamole. Sixty-one patients who underwent primary PTCA for treatment of acute anterior wall myocardial infarction were enrolled in this prospective study. Patients were divided into dipyridamole (DP) and nondipyridamole (non-DP) groups. The 2 groups had similar baseline characteristics. In the DP group, dipyridamole 0.5 mg/kg was infused intravenously for 3 minutes immediately before reperfusion during primary PTCA. Arrhythmias after reperfusion were analyzed from continuous ECG recordings. None of the patients in the DP group (n=23) had accelerated idioventricular rhythms (AIVR) or ventricular tachycardia (VT). In contrast, 7 (18.4%) had AIVR and 3 (7.9%) had VT in the non-DP group (n=38; P<0.01). Second, we tested for a termination effect of dipyridamole. Dipyridamole 0.5 mg/kg was infused intravenously while continuous ECG recordings were obtained in 9 patients who had either sustained AIVR (n=7) or sustained VT (n=2) after reperfusion of occluded coronary artery. Arrhythmias were terminated in all patients.

CONCLUSIONS

These results indicate that administration of dipyridamole can prevent and terminate reperfusion arrhythmias such as AIVR and VT. cAMP-mediated triggered activity may, at least in part, be responsible for reperfusion-induced AIVR and VT.

Electrophysiological mechanisms for ventricular arrhythmias in patients with myocardial ischemia: anesthesiologic considerations, Pt II

This is the second half of a two-part review article that discusses ventricular tachyarrhythmias, either induced by acute ischemia or consequent to chronic myocardial ischemia, and their anesthestic implications. The first half of the article was published in the June 1997 Issue of The Journal.

The Sicilian gambit. A new approach to the classification of antiarrhythmic drugs based on their actions on arrhythmogenic mechanisms. Task Force of the Working Group on Arrhythmias of the European Society of Cardiology

The Queen's Gambit is an opening move in chess that provides a variety of aggressive options to the player electing it. This report represents a similar gambit (the Sicilian Gambit) on the part of a group of basic and clinical investigators who met in Taormina, Sicily to consider the classification of antiarrhythmic drugs. Paramount to their considerations were 1) dissatisfaction with the options offered by existing classification systems for inspiring and directing research, development, and therapy, 2) the disarray in the field of antiarrhythmic drug development and testing in this post-Cardiac Arrhythmia Suppression Trial (CAST) era, and 3) the desire to provide an operational framework for consideration of antiarrhythmic drugs that will both encourage advancement and have the plasticity to grow as a result of the advances that occur. The multifaceted approach suggested is, like the title of the article, a gambit. It is an opening rather than a compendium and is intended to challenge thought and investigation rather than to resolve issues. The article incorporates first, a discussion of the shortcomings of the present system for drug classification; second, a review of the molecular targets on which drugs act (including channels and receptors); third, a consideration of the mechanisms responsible for arrhythmias, including the identification of "vulnerable parameter" that might be most accessible to drug effect; and finally, clinical considerations with respect to antiarrhythmic drugs. Information relating to the various levels of information is correlated across categories (i.e., clinical arrhythmias, cellular mechanisms, and molecular targets), and a "spread sheet" approach to antiarrhythmic action is presented that considers each drug as a unit, with similarities to and dissimilarities from other drugs being highlighted. A complete reference list for this work would require as many pages as the text itself. For this reason, referencing is selective and incomplete. It is designed, in fact, to provide sufficient background information to give the interested reader a starting frame of reference rather than to recognize the complete body of literature that is the basis for this article.

Multiform accelerated idioventricular rhythm (AIVR) in a child with acute myocarditis

Acute myocarditis is complicated by various types of conducting disturbances and heart failure. We describe the case of a school boy with acute myocarditis, who developed various types of conduction disturbances, including multiform accelerated idioventricular rhythm (AIVR), during convalescence from severe pump failure. Multiform AIVR has been reported mostly in adults but, to the best of our knowledge, not in children. The arrhythmia noted in our patient persisted for only 2 days and disappeared with recovery.

Control of cardiac arrhythmias by calcium antagonism

In recent years calcium channel blockers have emerged as a new class of antiarrhythmic agents for the control of certain supraventricular and ventricular arrhythmias. Electrophysiologically, they are heterogeneous but their main action is mediated through a depressant effect on the slow calcium channel in cardiac muscle. In isolated muscle, their actions are modulated by their reflex actions and by their interaction with the autonomic nervous system due to the nonocompetitive adrenergic blocking actions that some of the compounds exhibit. The major agents exerting antiarrhythmic actions are verapamil, diltiazem, gallopamil, tiapamil, and bepridil; the dihydropyridines are devoid of significant electrophysiologic actions in vivo. Calcium antagonists prolong intranodal conduction time, lengthen the effective and functional refractory periods in the AV node, but exert little or no effect on atrial, ventricular, His-Purkinje, or bypass tract conduction or refractoriness (except in the case of bepridil, which has additional electrophysiologic properties). These effects form the basis of the clinical antiarrhythmic effects of this class of agents. The most striking action is the predictable and prompt termination of reentrant supraventricular tachycardia by intravenous verapamil and diltiazem and the slowing of the ventricular response in atrial flutter and fibrillation. These agents may also be of value in the chronic control of ventricular response in atrial flutter and fibrillation; their role in multifocal atrial tachycardia and other ectopic tachycardias is less well defined. Calcium antagonists reverse ischemic ventricular arrhythmias due to coronary artery spasm but exert little or no action in the usual forms of sustained ventricular tachyarrhythmias associated with severe structural heart disease. They are poor suppressants of premature ventricular contractions. Recent data have established their role in exercise-induced tachycardia occurring in the context of ischemic heart disease; they are also of value in ventricular tachycardia occurring in young subjects developing tachycardia with a right bundle branch block with left axis deviation morphology, an arrhythmia thought to be due to triggered automaticity. The role of calcium antagonists in reducing the incidence of sudden death in the survivors of acute myocardial infarction remains uncertain.

Usefulness of the accelerated idioventricular rhythm as a marker for myocardial necrosis and reperfusion during thrombolytic therapy in acute myocardial infarction

The value of the accelerated idioventricular rhythm (AIVR) as a marker for myocardial necrosis and/or reperfusion was prospectively studied in 87 patients admitted with persistent ischemic chest pain. All patients received streptokinase. Necrosis was diagnosed by new Q waves and an increase in plasma enzymes. Reperfusion was documented angiographically. Myocardial necrosis occurred in 72 patients and reperfusion in 70 patients, 58 of whom had myocardial necrosis. Of 27 patients with AIVR, 26 had both necrosis and reperfusion (p less than 0.001). AIVR started after a long coupling interval to the preceding sinus rhythm and was regular. Configuration depended on the reperfused infarct vessel. Reperfusion of the left anterior descending branch showed most configurations of AIVR and with the least QRS width. Reperfusion of the circumflex branch never had a left bundle branch block-like configuration. AIVR from reperfusion of the right coronary artery never had an inferior axis. AIVR occurring during persistent ischemic chest pain is a marker for both myocardial necrosis and reperfusion of the infarct vessel. AIVR starts with a long coupling interval and is regular. The QRS configuration may be useful for the noninvasive identification of the infarct vessel.

Autonomic control of ventricular tachycardia: direct effects of beta-adrenergic blockade in 24 hour old canine myocardial infarction

The purpose of this study was to determine whether alpha- or beta-adrenergic influences directly modulate the rate of spontaneous ventricular tachycardia occurring 24 hours after left anterior descending coronary artery occlusion. Chloralose-anesthetized, open chest dogs (n = 41) with ventricular tachycardia were studied. The left anterior descending artery was cannulated distally. Neither intracoronary saline solution nor phenylephrine (0.3 to 12 micrograms) changed the rate of ventricular tachycardia; however, isoproterenol (0.01 to 10 micrograms) produced dose-dependent increases in the rate. In six dogs, metoprolol, 5 mg given intravenously, slowed ventricular tachycardia from 174 +/- 10 (mean +/- SE) to 140 +/- 17 beats/min (p less than 0.05). This was accompanied by decreases in mean arterial pressure from 106 +/- 7 to 95 +/- 8 mm Hg, cardiac output from 2.6 +/- 0.3 to 1.6 +/- 0.3 liters/min and prolongation of atrioventricular conduction from 134 +/- 10 to 189 +/- 29 ms (all p less than 0.05) during atrial pacing at a cycle length of 300 ms. In 10 dogs, metoprolol (0.5 mg) given intracoronary, a dose that shifted the isoproterenol dose-response curve to the right, slowed ventricular tachycardia from 174 +/- 7.2 to 140 +/- 9.7 beats/min (p less than 0.05) without hemodynamic changes. Additional metoprolol (4.5 mg) given intravenously produced hemodynamic alterations, but ventricular tachycardia did not slow further. Therefore, beta- but not alpha-adrenergic influences control the rate of ventricular tachycardia occurring 24 hours after left anterior descending coronary artery occlusion. Furthermore, beta-adrenergic blockade slows ventricular tachycardia solely by a direct electrophysiologic effect on the tachycardia foci and not indirectly as a result of hemodynamic effects.

Use of calcium antagonists for cardiac arrhythmias

Calcium antagonists have emerged as a new class of antiarrhythmic agents for the control of certain supraventricular and ventricular arrhythmias. Electrophysiologically, these agents are heterogeneous but their main action is mediated through a depressant effect on the slow calcium channel in cardiac muscle, most readily demonstrated in isolated tissue preparations. In vivo, their actions are modulated by their reflex actions and by their interaction with the autonomic nervous system due to the noncompetitive adrenergic-blocking actions that some of the compounds exhibit. The major agents exerting antiarrhythmic actions are verapamil, diltiazem, gallopamil, tiapamil and bepridil; the dihydropyridines are devoid of electrophysiologic actions in vivo. Calcium antagonists prolong intranodal conduction time, lengthen the effective and functional refractory periods in the atrioventricular node but exert little or no effect on atrial, ventricular, His-Purkinje or bypass tract conduction or refractoriness (except in the case of bepridil, which has additional electrophysiologic properties). These effects form the basis of the clinical antiarrhythmic effects of this class of agents. The most striking action is the predictable and prompt termination of the reentrant supraventricular tachycardia by intravenous verapamil and diltiazem and the slowing of the ventricular response in atrial flutter and fibrillation. These agents may also be of value in the long-term control of ventricular response in atrial flutter and fibrillation; their role in multifocal atrial tachycardia and other ectopic tachycardias is less well defined. Calcium antagonists reverse ischemic ventricular arrhythmias caused by coronary artery spasm but exert little or no action in the usual forms of sustained ventricular tachyarrhythmias associated with severe structural heart disease. They are poor suppressants of ventricular premature complexes. Recent data have established their role in exercise-induced tachycardia occurring in the context of ischemic heart disease; they are also of value in ventricular tachycardia occurring in young patients who develop tachycardia with a right bundle branch block and left axis deviation morphology, an arrhythmia thought to be due to triggered automaticity.

Calcium channel blocking agents and the heart

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Autonomic control of ventricular tachycardia: sympathetic neural influence on spontaneous tachycardia 24 hours after coronary occlusion

This study was performed to determine whether sympathetic nerves influence the rate of ventricular tachycardia occurring spontaneously in dogs 24 hr after occlusion of the anterior descending coronary artery. Seventeen chloralose-anesthetized dogs underwent activation mapping during spontaneous ventricular tachycardia with QRS morphologies similar to those recorded in the conscious state. Bilateral stellate ganglionectomy (n = 8) decreased mean arterial pressure from 71 +/- 4 (mean +/- SE) to 52 +/- 5 mm Hg (p less than .001) and heart rate from 121 +/- 9 to 79 +/- 15 beats/min (p less than .025) by decreasing the number of complexes of ventricular tachycardia from 120 +/- 9 to 49 +/- 15 per minute (p less than .001). Subsequent unilateral sympathetic nerve stimulation (n = 4) was shown to accelerate ventricular tachycardia foci originating from the ipsilateral aspect of the infarction. Regional sympathetic denervation (n = 7) was performed by application of phenol to the epicardium surrounding an electrode at the site of origin of at least one morphology of ventricular tachycardia. Mean arterial pressure did not change, but total heart rate decreased from 122 +/- 9 to 106 +/- 9 beats/min (p less than .01) and the number of complexes of ventricular tachycardia with a morphology arising from the phenol-treated area fell from 68 +/- 12 to 28 +/- 9 (p less than .001). Evidence for regional denervation was documented by prolongation of duration of electrograms and local repolarization times limited to the phenol-treated area. We conclude that sympathetic nerves directly control rate of spontaneous ventricular tachycardia 24 hr after myocardial infarction in the dog.