Potentiation of reperfusion-associated ventricular fibrillation by left ventricular hypertrophy.

Abstract

Important electrophysiological alterations that may predispose hearts to arrhythmias have been described for hypertrophied myocytes, and hypertrophy coupled with ischemia has been associated with an increased incidence of sudden death; however, an influence of hypertrophy on reperfusion arrhythmias has not been previously described. We hypothesized that reperfusion-associated arrhythmias would be potentiated by left ventricular hypertrophy. After induction of renovascular hypertension, 37 awake, unsedated dogs (17 with left ventricular hypertrophy and 20 without hypertrophy) underwent 15 minutes of coronary artery occlusion and reperfusion. All dogs were pretreated with lidocaine bolus injections and with lidocaine by continuous infusion during coronary occlusion and reperfusion. Reperfusion-associated ventricular fibrillation occurred in seven of 17 dogs with left ventricular hypertrophy versus one of 18 dogs without hypertrophy (p less than or equal to 0.05). The presence of hypertension was not significantly associated with an increased incidence of reflow ventricular arrhythmias. Neither QT interval nor area-at-risk was different between the dogs with and without reperfusion ventricular fibrillation; however, increased heart rate just before reperfusion did correlate with an increased incidence of ventricular fibrillation at reperfusion. Thus, 1) left ventricular hypertrophy was associated with a significantly increased incidence of reperfusion-induced ventricular fibrillation after 15 minutes of ischemia, 2) this increased incidence was independent of the presence of hypertension, and 3) lidocaine protected control and hypertrophied hearts against ventricular fibrillation during ischemia but was ineffective in protecting hypertrophied hearts against reperfusion-induced ventricular fibrillation.

Ischemia induces aggravation of baseline repolarization abnormalities in left ventricular hypertrophy: a deleterious interaction

“…HT not only is the most common cause of LVH, but it also accelerates the development of CAD and increases the oxygen demand, creating a highly life-threatening combination that is reflected by the associated increased incidence of SCD (34). According to experimental studies, there is a decreased tolerance to induced ischemia and reperfusion in myocardial hypertrophy (6,8,29,31,33). Several mechanistic factors have been identified, although their relative importance remains to be clarified.…”

“…Some patients with LVH, in particular those with hypertension, also have an increased propensity for developing CAD. Although experimental studies (see DISCUSSION) have shown reduced tolerance to ischemia and subsequent reperfusion in myocardial hypertrophy, including increased dispersion of repolarization, higher incidence of ventricular arrhythmias, and greater infarct size (6,8,29,31,33), the mechanistic interaction between LVH and ischemia has rarely been studied in humans. Because of these experimental observations, we focused on ventricular repolarization and its response to acute ischemia in a human model of coronary occlusion during percutaneous coronary intervention (PCI).…”

Is hypertensive left ventricular hypertrophy a cause of sustained ventricular arrhythmias in humans?

“…These chronic changes may produce a more arrhythmogenic milieu if epicardial CAD does develop. For example, dogs with hypertensive LVH undergoing left coronary artery occlusion had higher propensity for sustained monomorphic VT (41% vs. 6%; p < 0.05) and reperfusion-associated VF (88% vs. 0%; p < 0.05) compared to those that were normotensive; this disparity occurred despite infarct size being comparable across groups [ 18 , 19 ].…”

Susceptibility to Ischemia and Reperfusion Arrhythmias in Myocardial Hypertrophy Due to Flow of Injury Current?

“…1) Several animal studies 2,3) have demonstrated a powerful association between LV hypertrophy and fatal ventricular arrhythmias induced by ischemia and reperfusion. The increased risk of sudden cardiac death in patients with LV hypertrophy may be due to an increased susceptibility to ventricular arrhythmias.…”