Spectrum of haemodynamic responses to atrial pacing in coronary artery disease.

Atrial tachy-pacing was performed in 34 patients who were divided into 3 groups as follows. Group I: 4 patients with obscure chest pain syndromes and normal coronary arteries and haemodynamics; Group 2: 25 patients with significant coronary artery disease and angina pectoris; Group 3: 5 patients with coronary artery disease, left ventricular aneurysm, and left ventricular dysfunction. Pacing produced a reduction in the left ventricular stroke work index and the left ventricular end-diastolic pressure in Group i patients, while the cardiac index and the left ventricular minute work index showed no significant change. Group 2 patients showed a variety of responses. Nine patients had a 'normal' response to atrial pacing, namely a fall in left ventricular stroke work index and left ventricular end-diastolic pressure. Of these, .5 had experienced angina during pacing and 4 did not; the other I6 had abnormal responses. When considered as a group, there was a significant decrease in the left ventricular stroke work index and an increase in the left ventricular minute work index, while the left ventricular end-diastolic pressure and cardiac index did not change significantly. Group 3 patients demonstrated a significant fall in the left ventricular end-diastolic pressure and a rise in the cardiac index and the left ventricular minute work index, while the left ventricular stroke work index was unchanged. A reduction in the end-diastolic pressure without a fall in stroke work index and with an increase in the minute work index indicate improved myocardial performance in this group ofpatients. It is concluded that there is a wide spectrum of responses to atrial pacing ranging from no change in left ventricular function in some patients to gross dysfunction in others. Those with compromised left ventricular function exhibit improved performance.