Electrocardiographic antecedents of primary ventricular fibrillation. Value of the R-on-T phenomenon in myocardial infarction.

Abstract

Primary ventricularfibrillation was seen in 20 of 450 consecutive patients (4 4 %) admitted within 24 hours after the onset ofacute myocardial infarction. Compared withpatients withoutprimary ventricularfibrillation, they showed a lower mean age group and a higher incidence of anterior infarction. Waorning ventricular arrhythmias preceded primary ventricular fibrillation in 58 per cent of cases. However, warning arrhythmias were also present in 55 per cent ofpatients without primary ventricularfibrillation. Thefollowing mechanisms of initiation of primary ventricular fibrillation were seen. 1) In one patient, it was initiated by supraventricular premature beats showing aberrant intraventricular conduction. 2) In 2 patients, ventricular tachycardia degenerated into primary ventricular fibrillation. 3) In 17 patients, it was initiated by a ventricular premature beat; in 10 of these, the premature beat showed early coupling (RR'/QT<1-the R-on-T phnomenon). However, ventrcular premature beats showing the R-on-T phenomenon were also observed in 49 per cent of patients without pmary ventilar fibrillation. In 7, primary ventricular fibrllation was initiated by a late-coupled ventricular premature beat (RR'/QT>1); in 2, the very late coupling resulted in a ventricular fusion beat. The study suggests that waring arrhythmias and the R-on-T phenomenon are poor predictors ofprimary ventricularfibrillation in acute myocardial infarction. The observation that 41 per cent ofprimary ventricularfibrillation was initiated by a late-coupled ventricular premature beat suggests that ventricular vulnerability during acute myocardial infarction may extend throughout most of the cardiac cycle and is not necessarily confined to the QT interval.

Clinical Applications of Ambulatory Electrocardiography

“…Sudden death occurring during ambula tory electrocardiography has been reported by several groups [96][97][98][99][100], with potentially fatal arrhythmias often, but not invariably, associated with complex or early-cycle ven tricular cctopy in patients with ischemic or myopathic hearts [96. 98, 100], Other in stances of arrhythmic death have been asso ciated with late-cycle VPCs, particularly in patients with prolonged QT intervals [96,99,100], As classified by Hinkle and Thaler [101], arrhythmic death without prior circulatory collapse occurs commonly as a terminal event when heart disease is the primary cause of the final illness ( fig.…”

III Diretriz sobre tratamento do infarto agudo do miocárdio

“…O maior risco de fibrilação ventricular ocorre durante as primeiras 4h após o início dos sintomas 599,609 . A fibrilação ventricular observada na fase aguda (geralmente nas primeiras horas) do infarto, chamada de "fibrilação ventricular primária", ocorre em 4% a 18% dos pacientes com infarto [610][611][612] .…”

Early Intravenous Beta-blockers for Acute Myocardial Infarction

“…An electrocardiographic monitoring period of 48 h may be helpful in timely detection of ventricular arrhythmia based on the arrhythmia onset time window. Electrocardiogram information such as fragamented QRS wave21, QT interval prolongation [22,23], QT dispersion [24,25], T-wave alternans (TWA) and late potentials (LP) [26], reduced heart rate variability (HRV) [27] and R-on-T phenomenon [28] were demonstrated some value for predicting ventricular arrhythmia in patients with AMI. Also of great assistance in predicting ventricular arrhythmia were predictors such as left ventricular ejection fraction [29] and hapokalemia [30].…”