Diastolic time during low-level exercise in the late phase of hospitalization for acute myocardial infarction

To evaluate DT during a low-level exercise test, the relation between DT and heart rate was studied by ear densitography in the late phase of hospitalization for acute MI. None of the patients had an ischemic electrocardiographic response. The patients were divided into two groups: group 1 was comprised of nine patients with a resting left ventricular end-diastolic volume of 140 ml or more, and group 2 was comprised of nine patients with a left ventricular end-diastolic volume less than 140 ml. The QS2 and heart rate had an linear inverse relation during exercise, and DT and heart rate had an nonlinear inverse relation (DT = e(7.27-0.0166 x heart rate) and DT = e(7.11-0.0142 x heart rate) for groups 1 and 2, respectively). Significant prolongation of the QS2 with consequent shortening of DT (p less than 0.05) was observed in group 1. Thus, in addition to a larger decrease in DT with a small change in heart rate, particularly during low-level exercise, patients with increased left ventricular end-diastolic volume have a potential for initiating subendocardial ischemia which results in further prolongation of systole and, hence, greater abbreviation of DT.