Electromechanical changes in ischaemic heart disease

In coronary artery disease,. resting electrical and mechanical function of the left ventricle may vary according to different presentations. Stress or exercise in these patients results in electrical disturbances, which may havc mechanical consequences. The objectives ofthis thesis were: I) to assess the effect of the presence and location of Q wave myocardial infarction on left ventricular segmental mechanical function and identify patterns ofdisturbances. 2) to study the acute implications of induction of localised myocardial infarction at the proximal ventricular septum on ventricular performance. 3) to determine the effect of pharmacological stress on left and right ventricular behaviour in patients with coronary artery disease. AIl patients were studied by Doppler echocardiography using conventional measurements, as well as detailed assessment of long axis function and 12 lead surface EeG's. The foHowing groups ofpatients were studied: a). 72 patients with old Q wave MI; 35 anterior and 37 inferior. b) 54 patients with old anterior MI; 39 Q wave and 15 non-Q wave MI. c) 20 symptomatic patients with hypertrophic obstructive cardiomyopathy before and after non-surgical septal reduction therapy. d) . 27 patients with coronary artery disease, at rest and during dobutamine stress to assess left ventricular fune:tion. e) 33 patients with triple coronary artery disease at rest and at peak dobutamine stress to assess right ventricular function. The normal septal Q wave was' absent in 94% of anterior and 8% of inferior MI patients. Long axis amplitude and shortening and lengthening velocities were globaIly reduced in anterior and inferior myocardial infarction and the onset of shortening and lengthening were delayed by 30-40ms and 20-30 ms respectively in the two patient groups. Post ejection ~hortening was localised to the septum in the majority of patients with anterior myocardial infarction, but was generalised in patients with inferior infarction. 1) The normal septal Q wave was absent in 10% of control subjects and in 46% of patients with non-Q wave myocardial infarction. Q wave anterior MI was associated with a scarred septum and dilated LV cavity. Long axis amplitude was not different from normal in non-Q wave-infarction, but its onset ofshortening and lengthening was delayed by 20ms. Post ejection shortening occurred more frequently in Q wave infarction (76%) compared with non-Q wave infarction (21 %). These .abnormalities were localised to the left rand septal sites in non-Q wave infarction in contrast to their global distribution in Q wave infarction. . 2) Induction of localised upper septal myocardial infarction with alcohol resulted in broadening of the QRS (by 35ms), RBBB in 80% of patients, development of reduced septal long axis amplitude, and accentuated post ejection shortening at the septal long axis site. 3) In contrast to controls, dobutamine stress results in progressive broadening of QRS duration and prolongation of the QTc interval in patients with coronary artery disease, with corresponding reductions in long axis amplitude of motion and peak lengthening .velocity. 4) In patients with triple vessel coronary disease, dobutamine stress results in right ventricular long axis ischaemic disturbances similar to those seen on the left. Failure ofright ventricular long axis amplitude to increase by 2 mm was 88% specific for detecting right ventricular ischaemic dysfunction, which also correlated with the attenuated cardiac output at peak stress r= 0.56, p