Mechanisms of slow ventricular tachycardias in acute myocardial infarction

Clinical characteristics and therapeutic strategy of frequent accelerated idioventricular rhythm

Background

Accelerated idioventricular rhythm (AIVR) is often transient, considered benign and requires no treatment. This observational study aims to investigate the clinical manifestations, treatment, and prognosis of frequent AIVR.

Methods

Twenty-seven patients (20 male; mean age 32.2 ± 17.0 years) diagnosed with frequent AIVR were enrolled in our study. Inclusion criteria were as follows: (1) at least three recordings of AIVR on 24-h Holter monitoring with an interval of over one month between each recording; and (2) resting ectopic ventricular rate between 50 to 110 bpm on ECG. Electrophysiological study (EPS) and catheter ablation were performed in patients with distinct indications.

Results

All 27 patients experienced palpitation or chest discomfort, and two had syncope or presyncope on exertion. Impaired left ventricular ejection fraction (LVEF) was identified in 5 patients, and LVEF was negatively correlated with AIVR burden (P < 0.001). AIVR burden of over 73.8%/day could predict impaired LVEF with a sensitivity of 100% and specificity of 94.1%. Seventeen patients received EPS and ablation, five of whom had decreased LVEF. During a median follow-up of 60 (32, 84) months, LVEF of patients with impaired LV function returned to normal levels 6 months post-discharge, except one with dilated cardiomyopathy (DCM). Two patients died during follow-up. The DCM patient died due to late stage of heart failure, and another patient who refused ablation died of AIVR over-acceleration under fever.

Conclusions

Frequent AIVR has unique clinical manifestations. AIVR patients with burden of over 70%, impaired LVEF, and/or symptoms of syncope or presyncope due to over-response to sympathetic tone should be considered for catheter ablation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12872-021-02221-0.

The role of cardiac magnetic resonance imaging (cardiovascular magnetic resonance) in defining the prognosis of patients with acute ST-segment elevation myocardial infarction. Part 1. Indications and contraindications to cardiovascular magnetic resonance

Recently, the role of cardiac magnetic resonance imaging (cardiovascular magnetic resonance) in the diagnosis of coronary artery disease and acute myocardial infarction has increased significantly. This method is defined as the gold standard for differentiation between ischemic vs non-ischemic and acute vs chronic myocardial injury. This part of the review summarizes the main methods of cardiovascular magnetic resonance, its safety, indications and contraindications.

Correlations between clinical and laboratory findings and prognostically unfavorable CMR-based characteristics of acute ST-elevation myocardial infarction

Aim To evaluate factors associated with unfavorable predictive characteristics of ST-segment elevation acute myocardial infarction (STEMI) as per data of magnetic resonance imaging (MRI).Material and methods The study included 52 patients with STEMI who underwent a primary percutaneous coronary intervention (pPCI). Contrast-enhanced cardiac MRI was performed for all patients on days 3-7. Delayed contrast-enhancement images were used for assessing infarct size, presence of microvascular obstruction (MVO) areas, and heterogeneity zones.Results Multifactorial analysis showed that independent predictors of MVO were type 2 diabetes mellitus (DM) (relative risk (RR) 1.9, confidence interval (CI): 1.1-3.26, р=0.012), increased levels of brain natriuretic peptide (BNP) (RR 2.04, CI: 1.39-2.99, р=0.004) and creatine kinase (CK) (RR 2.06, CI: 0.52-0.80, р=0.02), and infarct size (IS) (RR 2.81; CI: 1.38-5.72, р=0.0004). Construction of ROC curves provided the quantitative values of study indexes, at which the risk of MVO increased. For BNP, this value was ≥276 pg/ml (sensitivity, 95.7 %; specificity, 37.9 %); for CK ≥160 U/l (sensitivity, 74.1 %; specificity, 61.9 %); and for IS ≥18.8 % (sensitivity, 79.3 %; specificity, 69.6 %). Correlation analysis of risk factors for increased size of the heterogeneity zone showed significant correlations of the heterogeneity zone size with older age of patients (r=0.544, р&lt;0.0001), higher concentrations of BNP (r=0.612, р&lt;0.0001), CK (r=0.3, 95 % CI: 0.02-0.5, р=0.03), and C-reactive protein (CRP) (r=0.59, CI: 0.3-0.7, р=0.0001). Increased levels of CK (r=0.53, 95 % CI: 0.29-0.70, р=0.0001) and BNP (r=0.55, 95 % CI: 0.28-0.70, p=0.0003) significantly correlated with increased IS.Conclusion Risk of MVO formation as per MRI data increased in the presence of type 2 DM and IS ≥18.8 % (р&lt;0.05). Formation of MVO in patients with STEMI was associated with increased levels of BNP ≥276 pg/ml and CK ≥160 U/l (р&lt;0.05). Increased levels of BNP, CK, and CRP were associated with a larger size of heterogeneity zone according to data of the correlation analysis. A larger heterogeneity zone was more typical for older patients. Increased levels of CK and BNP were also associated with larger IS. The correlation analysis did not show any significant interactions between the size of heterogeneity zone, IS, and MVO size (р&gt;0.05).

Accelerated Idioventricular Rhythm in Inflammatory Bowel Disease: When the Gut Takes Charge

Accelerated idioventricular rhythm (AIVR) is an uncommon but benign rhythm, seen most commonly in children. It is associated with reperfusion injury after myocardial infarction in adults. In children, it is usually seen as an idiopathic finding in the absence of heart disease. We present a case of AIVR in an adolescent associated with acute presentation of inflammatory bowel disease. Prompt treatment of the systemic inflammation led to the remission of both inflammatory bowel disease and AIVR. This report emphasizes the diverse causes of AIVR in children and our limited understanding of its pathophysiology. Treatment of the underlying condition resolved the arrhythmia.

Transient post-reperfusion left bundle branch block and accelerated idioventricular rhythm with paradoxical QRS narrowing

Accelerated idioventricular rhythm (AIVR) commonly follows coronary reperfusion and has been called a "reperfusion arrhythmia". Transient left bundle branch block (LBBB) is only rarely seen after interventional reperfusion and is usually considered a procedural complication. We report herein electrocardiograms (ECGs) in a case of acute lateral myocardial infarction which demonstrate both post-perfusion AIVR and a simultaneous transient LBBB with fusion complexes causing paradoxical QRS narrowing.

Catheter ablation of long-lasting accelerated idioventricular rhythm in a patient with mild left ventricular dysfunction

A 35-year-old woman with long-lasting accelerated idioventricular rhythm (AIVR) exhibited palpitation and dyspnea on exertion and mild left ventricular (LV) dysfunction during followup. Symptoms appeared 10 years after the AIVR was first noted, and she underwent catheter ablation for curative therapy of AIVR after 12 years. Radiofrequency ablation of the anteroseptal site of the LV at the earliest activation terminated rhythm. An echocardiogram, taken 1 month after discharge, subsequently revealed that the left ventricular wall motion had normalized. This is a rare case of long-lasting AIVR with mild LV dysfunction.

Accelerated idioventricular rhythm detected during elective surgery in a healthy man

Accelerated idioventricular rhythm (AIVR) is found most commonly in the presence of underlying heart disease. It is characterized by acceleration of a latent pacemaker that normally depolarizes slowly. We describe a 30-year-old man who was found to have episodes of accelerated idioventricular rhythm (AIVR) on cardiac monitoring during elective orthopedic surgery. Noninvasive evaluation including two-dimensional echocardiography was unremarkable. No late potentials were detected on a signal-averaged electrocardiogram. During an exercise tolerance test, AIVR was suppressed as heart rate increased. A 24-h Holter monitor revealed that the AIVR rate was consistently 73-76 beats/min, which appeared whenever the sinus rate slowed to this level. The patient has been asymptomatic, and the rhythm has persisted at least through a 5-month follow-up period.

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.

Extra AV nodal Wenckebach periodicity

Extra AV nodal Wenckebach periodicity was diagnosed in seven patients. The most frequent form of this conduction abnormality was an exit block. The underlying block was localized in the sinoatrial junction and in the atria in two patients; the AV junction and the ventricle were the site of the Wenckebach periodicity in one case each. In extra AV nodal exit block, the actual conduction delay is not seen on the ECG and the diagnosis is based on the progressive shortening of the P-P or R-R intervals followed by a pause which is less than twice the shortest P-P (R-R) interval depending on the level of the block. A Wenckebach periodicity in the bundle branches or within the reentry pathway each occurred in one patient. In these forms of Wenckebach periodicity, the diagnosis is established more readily because the conduction delay can be demonstrated on the surface ECG. The clinical significance of extra AV nodal Wenckebach periodicity is discussed.

Slow ventricular tachycardia complicating acute myocardial infarction

Among 200 consecutive cases of acute myocardial infarction (AMI) treated in a CCU, 117 episodes of slow ventricular tachycardia were observed in 72 patients. This figure represents a 36% rate of incidence. It is a relatively high figure because of the close monitoring to which the patient is submitted and because of the early admission to the unit. There were no significant differences of age, sex, or localization of the myocardial necrosis between patients with SVT and those without it. The different mechanisms of production described support an active origin in most of the patients for the following reasons: (1) coexistence of SVT and PVT in 51.3% of the patients; (2) identical QRS morphology in both rhythms; (3) onset of the SVT after a nonprolonged diastole in 70% of the tracings; (4) inhibition of the SVT after increase of the sinus discharge in only 14 occasions; and (5) irregular SVT rhythm in 76.9% of the recordings and ectopic mechanisms with different degrees of exit block. Because of the potential hazard of the SVT, especially if it is assumed to be of an active origin, we recommend lidocaine for patients with a sinus rate faster than 60 per minute or coexisting PVT. Atropine should be used when the sinus rate is slower than 60 per minute assuming a possible escape or passive origin.

Disorders of cellular electrophysiology produced by ischemia of the canine His bundle

In the first 4 hours after occlusion of the anterior septal coronary artery, 18 dogs developed bundle branch block, heart block, or both. The hearts were then excised, and preparations were dissected to expose the His bundle and the bundle branches, which were superfused with modified Tyrode's solution at 37 degrees C. In the His bundle and the most proximal bundle branches, resting potentials were reduced and diminutive action potentials had slow upstrokes, often with notches or steps. Action potentials were generated by fibers that had resting potentials between--40 and --50 mv. Conduction was impaired; conduction velocities less than 0.01 m/sec were sometimes observed. In more severely affected cells, refractoriness outlasted repolarization. Encroachment on the prolonged refractory period resulted in further diminution of action potentials and continuous rather than intermittent block. More commonly, the response to rapid rate took the form of intermittent block with progressive conduction delay in the series of conducted beats, culminating in a blocked beat (Wenckebach sequence). There was a fatigue factor that accumulated at short cycle lengths and depressed the action potential. Automaticity was not enhanced, but pacemaker function was abnormal. The threshold potential shifted erratically, and pacemaker potentials sometimes were intermittently diminished, resulting in intermittent failure to propagate. During prolonged superfusion, there was a tendency to recover with a drift of the maximum diastolic potentials toward more negative levels. None of these changes were found in ten hearts excised from dogs in which the coronary artery had not been ligated.

Incidence and description of accelerated ventricular rhythm complicating acute myocardial infarction

One hundred and nineteen episodes of accelerated ventricular rhythm (less than 125/min) were noted in 37 patinets with acute myocardial infarction during a 1 year period. The incidence was 12.7 per cent. Twenty-seven episodes of fast ventricular tachycardia (less than 125/min) were noted in 16 of these patients. Eighteen patients had anterior myocardial infarction and 19 inferior myocardial infarction. The mechanism of onset of accelerated ventricular rhythm was classified as escape in 65 episodes. Ventricular premature beats were noted close to episodes of accelerated ventricular rhythm in 31 patients and fast ventricular tachycardia in 14 patients. The morphology of accelerated ventricular rhythm was similar to the ventricular premature beats in 27 patients and similar to the fast ventricular tachycardia in 12. In 11 patinets the morphology of ventricular premature beats, accelerated ventricular rhythm and fast ventricular tachycardia were all the same. In six patients the coupling time of the ventricular premature beats and the onset of the accelerated ventricular rhythm were the same. In seven patients the morphology of the accelerated ventricular rhythm and fast ventricular tachycardia were the same, and the rate of the accelerated ventricular rhythm was exactly half that of the fast ventricular tachycardia. There were three deaths due to shock and heart failure. Three episodes of fast ventricular tachycardia progressed to ventricular fibrillation and were successfully cardioverted. It is concluded that accelerated ventricular rhythm and fast ventricular tachycardia were all the same. In six patients the coupling time of the ventricular premature beats and the onset of the accelerated ventricular rhythm were the same. In seven patients the morphology of the accelerated ventricular rhythm and fast ventricular tachycardia were the same, and the rate of the accelerated ventricular rhythm was exactly half that of the fast ventricular tachycardia. There were three deaths due to shock and heart failure. Three episodes of fast ventricular tachycardia progressed to ventricular fibrillation and were successfully cardioverted. It is concluded that accelerated ventricular rhythm is a relatively common complication of both anterior and inferior myocardial infarction. The high incidence of concomitant fast ventricular tachycardia, the frequency of ventricular premature beats with similar morphology and coupling time, and the instances of two arrhythmias having common rate multiples, suggest that at least in some instances accelerated ventricular rhythm may represent an ectopic focus with exit block.

Sustained accelerated idioventricular rhythm

A 73-year-old white man became easily fatigued and hypotensive six weeks after a documented acute inferior myocardial infarction. Continuous ECG monitoring showed a sustained tachycardia with a right bundle branch block pattern. A His bundle electrogram showed no His deflection prior to ventricular activation. The patient was successfully treated with intravenous procaine amide resulting in reversion to sinus rhythm, loss of symptoms, and return of blood pressure to normal levels. The unique aspects of this case and therapeutic considerations in the management of this problem are discussed.

Idioventricular tachycardia with angina pectoris

Idioventricular tachycardia (IVT) occurred in a patient with angina pectoris on three separate occasions associated with stress induced angina. It occurred immediately after a Master's test, a treadmill exercise test, and following an episode of paroxysmal atrial tachycardia which was precipitated by endocardial pacing. His bundle electrograms demonstrated that the rhythm was ventricular in origin. Cardiac catheterization documented the presence of severe coronary artery disease. Idioventricular tachycardia is often seen with acute myocardial infarction. It is rarely seen with angina or with exercise testing. To our knowledge this is the first reported case of IVT which could be repeatedly produced by stress induced angina.

A comparison of transmural and nontransmural acute myocardial infarction

The records of one hundred and four patients who had enzyme curves diagnostic for acute myocardial infarction (MI) were analyzed to determine what differences, if any, existed between the clinical course of patients with transmural myocardial infarction (TMI) and patients with nontransmural myocardial infarction (NTMI). The patients were subdivided into the two groups on the basis of accepted electrocardiographic criteria. There were no significant differences in prevalence or type of arrhythmias, occurrence of cardiogenic shock, or mortality in the hospital between the two groups. Enzymes tended to be somewhat lower in those with NTMI than in those with TMI. Clinical congestive heart failure (CHF) occurred more frequently in patients with TMI than in those with NTMI. Therefore, determining by electrocardiographic criteria whether or not a MI is transmural or nontransmural does not make it possible to predict the outcome or pattern of complications in a patient with acute myocardial infarction.

Electrophysiologic studies during accelerated idioventricular rhythms

Accelerated idioventricular rhythms (AIVR) are ectopic ventricular rhythms with rates intermediate between idioventricular escape rhythms (30 to 40/min) and ventricular tachycardia (120 to 180/min). Differentiation of AIVR from supraventricular arrhythmias rests primarily on demonstration of their ventricular origin. His bundle electrograms (HBE) were recorded in four patients during AIVR. HBE verified the idioventricular nature of the ectopic rhythm and excluded supraventricular rhythm with aberration as a cause. In addition, they permitted the recognition of normally conducted sinus beats, fusion beats, and idioventricular beats. The pacemaker site for the AIVR was below the bundle of His. AIVR became manifest when the heart rate was slowed by increasing vagal tone, premature atrial stimulation, and high degree atrioventricular (A-V) block. AIVR could be suppressed and 1:1 A-V conduction established by increasing the atrial rate with atropine or by atrial pacing.

Prevention and treatment of ventricular dysrhythmias

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