Sustained ventricular tachycardia as a marker of inadequate myocardial perfusion during the acute phase of myocardial infarction

Predictors of ventricular tachyarrhythmia in high-risk myocardial infarction patients treated with primary coronary intervention

Background. We investigated the association between clinical characteristics, angiographic data and ventricular arrhythmia in patients with ST-elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI)Methods. In patients with STEMI (n=225), a Holter analysis was performed the first 12 hours after primary PCI.Results. A total of 151 (66%) patients had >/=1 episode of ventricular tachycardia (VT). Age <70 years (RR 4.9, 95% CI 1.8 to 12.7), TIMI 0-1 pre-PCI (RR 2.6, 95% CI 1.1 to 6.1) and peak CK (RR 3.5, 95% CI 1.9 to 5.8) were independent predictors of VT. One-year mortality was 7%, no association between mortality and presence of early VT was found.Conclusion. Ventricular tachycardia is common in the first 12 hours after primary PCI for STEMI. Independent predictors of VT are younger age, TIMI 0-1 flow prior to PCI and larger infarct size. The presence of early VT was not significantly associated with one-year mortality. (Neth Heart J 2010;18:122-8.).

Could sustained monomorphic ventricular tachycardia in the early phase of a prime acute myocardial infarction affect patient outcome?

OBJECTIVES

Sustained monomorphic ventricular tachycardia (SMVT) in the course of a prime acute myocardial infarction is not a common arrhythmia and its prognostic significance has not been specifically elucidated. The aim of the study was to estimate the prognostic implications of the occurrence of sustained monomorphic ventricular tachycardia in the early phase (<72 h) of a prime acute myocardial infarction.

METHODS

We studied 690 consecutive patients admitted to the coronary care unit with a diagnosis of a prime myocardial infarction. SMVT was observed in 18 (2.6%) patients and we followed these patients for establishing the prognostic value of the arrhythmia according to the clinical characteristics.

RESULTS

Patients with SMVT had a more extensive myocardial infarction based on the peak of the CK-MB isoenzyme activity (480+/-290 IU/L, vs 270+/-190 IU/L, P < .01), and higher mortality rate (40% vs 9%, P < .001). The independent predictors of SMVT were CK-MB (odds ratio [OR] 12.4), presence of complex ventricular arrhythmias (OR = 5.7), a wide QRS complex > or =130 milliseconds (OR = 4.8) and Killip class (OR = 4.8). The SMVT was itself an independent predictor of mortality (OR = 5.0). Compared with patients with ventricular fibrillation or polymorphic ventricular tachycardia, those with SMVT had a higher CK-MB activity, higher rate of wide QRS > or =130 milliseconds (33% vs 8%, P < .002), had a worse hemodynamic condition (Killip class >I:58% vs 23%, P < .04) and higher recurrence rate of ischemic events (68% vs 16%, P < .05). During the one year follow-up period, 4 patients (36.3%) of the 11 survivors from those with SMVT died of cardiac related causes.

CONCLUSIONS

SMVT during the first 72 h of a prime myocardial infarction is an index of a larger healing myocardium with acute very complexed electrophysiological changes and it is an independent predictor of in-hospital mortality and a prognostic factor of a poor one year outcome.

Ventricular arrhythmias after acute myocardial infarction: a 20-year community study

BACKGROUND

Although myocardial infarction (MI) severity is declining, the occurrence of ventricular arrhythmia (VA) after MI and its effect on outcome is unknown. This study was undertaken to examine the frequency and timing of VA and the effect of VA on mortality after MI.

METHODS

Myocardial infarctions recorded between 1979 and 1998 were validated. Baseline characteristics, occurrence of VA, and survival were determined. Ventricular arrhythmias were categorized as primary ventricular fibrillation (VF), nonprimary VF, and ventricular tachycardia (VT). Logistic regression was used to analyze associations between VA and baseline characteristics. Temporal trends were assessed with the Mantel-Haenszel chi2. Survival was analyzed with the Kaplan-Meier method. Proportional hazards regression was used to examine the association between death and occurrence of VA.

RESULTS

Among 2317 persons with incident MI, 7.5% experienced VA (3.6% nonprimary VF, 2.1% primary VF, 1.8% VT). Ventricular arrhythmia-associated factors were younger age, female sex, higher Killip class, ST elevation, and atrial fibrillation. Ventricular arrhythmias were associated with increased risk of death at 30 days.

CONCLUSION

Ventricular arrhythmias after MI are relatively common, particularly among persons with more severe MI and no prior history of coronary disease. Over time, the incidence of VF declined, whereas VT did not change. Ventricular arrhythmia after MI was associated with a 6-fold increase in morality. Thus, identification of high-risk MI survivors and prevention of VA could markedly improve outcomes. Further studies are needed to determine the cause of the shift in distribution of VA subtype.

Optical mapping of the functional reentrant circuit of ventricular tachycardia in acute myocardial infarction

OBJECTIVES

We used optical mapping to characterize the reentrant circuit of ventricular tachycardia (VT) during acute myocardial infarction (MI) in isolated canine left ventricular preparations.

BACKGROUND

The nature of the reentrant circuit that underlies VT during acute MI is not well understood.

METHODS

Using optical mapping in isolated canine left ventricular preparations, we characterized the reentrant circuit of monomorphic VT (mean cycle length 245.3 +/- 15.6 ms, n = 7) induced by programmed stimulation during acute MI.

RESULTS

Optical mapping during VT revealed a functional reentrant circuit consisting of four components: (1) a protected isthmus located between the infarction area and the functional line of block; (2) an entrance site located at one end of the isthmus; (3) an exit site located at the other end of the isthmus; and (4) an outer loop consisting of nonischemic normal tissue, connecting the exit and entrance sites. Rate-dependent slow conduction within the border zone was associated with significant changes (n = 6) in action potential amplitude (99.1 +/- 0.4 vs 71.4 +/- 0.6 mV, P < .01), maximal diastolic potential (-80.6 +/- 0.2 vs -65.4 +/- 0.6 mV, P < .05), action potential duration at 90% repolarization (APD(90); 188.4 +/- 1.0 vs 164.3 +/- 3.1 ms, P < .05), and dV/dt (302.4 +/- 7.9 vs 168.5 +/- 3.6 V/s, P < .05). Compared to preparations with no inducible VT (n = 7), formation of a functional line of block was the key mechanism for initiation of functional reentry in preparations with VT. When comparing preparations with sustained and nonsustained VT, preservation of slow conduction over the isthmus was the key component for maintenance of sustained VT.

CONCLUSIONS

The reentrant circuit of monomorphic VT in the setting of acute MI involved both the infarction border zone and nonischemic normal tissue. The underlying mechanism is related to the presence of rate-dependent slow conduction and the development of a functional line of block in the border zone.

Reduction of "no-reflow" phenomenon by intra-aortic balloon counterpulsation in a randomized magnetic resonance imaging experimental study

OBJECTIVES

Intra-aortic balloon counterpulsation (IABC) can improve post-myocardial infarction (MI) outcomes, but the mechanisms of such effect remain unclear. We hypothesized that IABC augmentation reduces the extent of microvascular obstruction after acute infarction.

BACKGROUND

Microvascular obstruction or "no-reflow" (MO) has been shown to negatively influence left ventricular (LV) remodeling after myocardial infarction (MI).

METHODS

Seventeen dogs underwent 90 min of coronary artery occlusion followed by reperfusion. Animals were then randomized to either IABC (n = 9) or control (n = 8); IABC augmentation was performed for 24 h after MI. Microvascular obstruction and infarct size by first-pass and delayed contrast-enhanced magnetic resonance imaging (MRI) were measured at 1 and 24 h after reperfusion and compared with postmortem infarct size and MO by microspheres.

RESULTS

Microvascular obstruction by MRI, expressed as percent LV mass, decreased significantly in IABC (4.9 +/- 2.2% to 3.6 +/- 1.5%) and increased in controls (3.4 +/- 0.5% to 4.9 +/- 1.1% from 1 to 24 h, respectively; p < 0.001). Similar results were found for MO defined by microspheres. In the control group, MO increased significantly, during 24 h of study (from 8.8 +/- 1.7% to 43.2 +/- 11.1% of infarcted myocardium; p < 0.05), whereas not important change was observed in the IABC group (from 21.3 +/- 7.1% to 25.8 +/- 14.7%; p < 0.05 vs. control at 24 h). Infarct size, measured by MRI, increased in both groups (13.2 +/- 1.8 to 15.5 +/- 2.1 from 1 to 24 h, respectively; p < 0.05).

CONCLUSIONS

Intra-aortic balloon counterpulsation augmentation performed after reperfusion improves myocardial perfusion at the tissue level, and reduces the extent of no-reflow caused by microvascular obstruction.