Myocardial cell membrane stress ionic dyskinesia reversal by diltiazem.

Based on previous observations of cardioplegic ionic myocardial distress, myocardial stress dyskinesia was investigated as another possible cause of exercise stress testing-induced silent myocardial ischemia by analyzing the efficacy of the myocytic calcium channel blocker diltiazem in normalizing the results of patients who previously tested positive.From October 2004 to February 2006, 25 patients (13 women [52%]; aged between 28 and 71 years; mean age 56.9 years) complaining of precordial pain, with no coronary artery obstruction detected by scintigraphy and coronary cineangiography studies, presenting with positive ergometric testing, defined by ST segment depression, with no precordial pain or arrhythmia during testing, were treated with diltiazem in three daily doses of 90 mg, and were restudied five or seven days after the first examination. Treadmill electrocardiography exercise testing was performed using the standard Bruce protocol, analyzing the following parameters: the J point and Y point of the ST segment depression, maximum oxygen uptake reached, heart rate, double product and exercise performance measured in metabolic equivalents.The administration of diltiazem abolished patients' complaints of atypical precordial pain in all cases and blocked ST segment depression, both J point (control: mean 2.3+/-0.5 mm; with treatment: 0.4+/-0.5 mm; P<0.001) and Y point (control: mean 1.9+/-0.7 mm; with treatment: 0.1+/-0.3 mm; P<0.001). The heart rate variations were not significant (P>0.05), with mean values of 156.2+/-12.0 beats/min for the control and 149.0+/-19.2 beats/min with treatment. There was significant (P<0.01) improvement in the functional classification of the heart with treatment (mean 2.7+/-0.9 for the control and 2.0+/-0.7 with treatment), without significant variations (P>0.05) in maximum oxygen uptake and double product results.The administration of the myocytic calcium channel blocker diltiazem impeded the occurrence of the silent ST segment depression, previously induced by exercise stress testing in patients without confirmed obstructive coronary artery disease, supporting the involvement of calcium-dependent myocardial contraction ionic dyskinesia in the genesis of silent ST segment depression.