The insufficient nitrate response: patients' characterization and response to beta and calcium blockade

Abstract

Little information has been published regarding the nitrate-induced changes of left ventricular volumes at rest and during exercise in relation to the degree of the anti-ischaemic response. Therefore we assessed the electrocardiographically defined nitrate response to a single tablet of 80 mg isosorbide dinitrate s.r. and compared it to the changes in end-diastolic volumes at rest and during exercise, as determined by radionuclide ventriculography. Thirty-four of the 63 patients were classified as good nitrate responders, whereas 29 patients showed insufficient nitrate response with regard to the reduction of exercise-induced ST-segment depression. The baseline characteristics were quite comparable. At rest the ISDN-induced decrease of the end-diastolic count rate was significantly less (-17%) in patients with insufficient ST-segment response when compared to patients with good ST-segment response (-25%). During exercise, in patients with good ST-segment response, ISDN reduced the end-diastolic volume significantly (-19%), whereas in patients with insufficient ST-segment response the end-diastolic volume remained unchanged. In this special subset of patients with insufficient nitrate response we further evaluated the effects of additional beta or/and calcium blockade. The benefits from verapamil were equivalent to propranolol. However, a considerable part of the patients investigated needed the combination of verapamil and propranolol for an optimal anti-ischaemic drug treatment. Thus, our data support the concept that preload reduction plays a major role for the anti-ischaemic effects of ISDN in patients with exercise-dependent ischaemia. Since, a suboptimal therapeutic effect must be considered, objective control of the nitrate therapy (usually by exercise- and Holter-ECG) must be regarded as obligatory for each individual patient if optimal results are to be expected.

Acute Effects of Oral Isosorbide Dinitrate on Exercise Thallium-201 Myocardial Imaging in Patients with Stable Angina Pectoris

“…These raise the possibility that changes in average count density may be related to changes in left ventricular geometry, in the presence of unaltered perfusion. semi-upright ergometry and gated radionuclide angiocar diography; it was noted that the patients with insufficient nitrate response were the ones who did not develop a decrease in their left ventricular end diastolic volume [36]. It is conceivable that ISDN in our patients effected a reduction of myocardial oxygen demands through signifi cant decrement of left ventricular volume.…”