[Time of occurrence of primary ventricular tachycardia in the acute phase of myocardial infarction].

The hour of day of primary ventricular tachycardia (VT) in the acute phase of myocardial infarction was studied in 63 consecutive patients without cardiac failure or antiarrhythmic therapy, admitted to hospital less than 6 hours after the onset of chest pain. There were 19 women and 44 men, with an average age of 63 years. The site of infarction was anterior in 23 cases, posterior in 34 cases and circumferential in 6 cases. The cardiac rhythm was analysed from the 6th hour following the onset of chest pain for 4 days, using a HP 98220 A computerised analyser CPK levels were measured daily. Ventricular tachycardia occurred in 73% of cases with no significant difference between daytime (18 patients) and night time (28 patients). The patients developing VT did not differ from the remainder with respect to age, sex, or site of ECG changes, but peak CPK levels were significantly higher than in patients without VT. The risk of VT decreased slowly as the interval from the onset of chest pain increased and fell practically to zero after the 40th hour. Diurnal and nocturnal VT were independent of age, sex or site of infarct. However, nocturnal VT correlated independently of the time of onset of chest pain to high values of CPK. There was no difference with respect to age, sex, location of infarct or incidence of ventricular tachycardia between infarcts with pain starting during the day, and infarcts with pain starting at night. However, when the pain started during the day, the peak CPK was significantly higher and there were significantly more attacks of nocturnal ventricular tachycardia.(ABSTRACT TRUNCATED AT 250 WORDS)