Silent myocardial ischemia

Ambulatory and silent myocardial ischemia in women with coronary microvascular dysfunction: Results from the Cardiac Autonomic Nervous System study (CANS)

BACKGROUND

Up to two-thirds of patients with obstructive coronary artery disease (CAD) have silent ischemia (SI), which predicts an adverse prognosis and can be a treatment target in obstructive CAD. Over 50% of women with ischemia and no obstructive CAD have coronary microvascular dysfunction (CMD), which is associated with adverse cardiovascular outcomes. We aimed to investigate the prevalence of SI in CMD in order to consider it as a potential treatment target.

METHODS

36 women with CMD by coronary reactivity testing and 16 age matched reference subjects underwent 24-h 12-lead ambulatory ECG monitoring (Mortara Instruments) after anti-ischemia medication withdrawal. Ambulatory ECG recordings were reviewed by two-physician consensus masked to subject status for SI measured by evidence of ≥1 minute horizontal or downsloping ST segment depression ≥1.0 mm, measured 80 ms from the J point.

RESULTS

Demographics, resting heart rate, and systolic blood pressure were similar between CMD and reference subjects. Thirty-nine percent of CMD women had a total of 26 SI episodes vs. 0 episodes in the reference group (p = 0.002). Among these women 13/14 (93%) had SI, and few episodes (3/26, 12%) were symptomatic. Mean HR at the onset of SI was 96 ± 13 bpm and increased to 117 ± 16 bpm during the ischemic episodes. 87% reported symptoms that were not associated with ST depressions.

CONCLUSIONS

Ambulatory ischemia is prevalent in women with CMD, with a majority being SI, while most reported symptoms were not accompanied by ambulatory ischemia. Clinical trials evaluating anti-ischemic medications should be considered in the CMD population.

Can nitroglycerin convert effort-induced angina in men into silent myocardial ischemia?

The relief of anginal pain with nitroglycerin may not correspond to the disappearance of ischemia. To evaluate the possible lack of the elimination of ischemia with sublingual nitroglycerin, we studied 25 male patients with stable angina pectoris who underwent exercise stress testing with recording of blood pressure, pulse, and ST-segment displacement. The stress test was repeated 30 minutes after administration of 0.4 mg of sublingual nitroglycerin. All 25 patients had angina and ischemic ST-segment changes in the first stress test. On repeat stress testing, 15 patients had angina and ST-segment changes, 2 patients had angina but no ST-segment changes, and 4 patients had no ST-segment changes and no angina. Four patients, however, had no angina but persistent ischemic ST-segment changes suggesting that angina was converted into silent ischemia. The mean exercise duration was 311 +/- 66 seconds before and 421 +/- 81 seconds after the nitroglycerin test. Peak heart rate and systolic blood pressure before the nitroglycerin stress test were 109 +/- 18 and 155 +/- 23 mm Hg; in the repeat stress test, they increased to 123 +/- 21 and 162 +/- 20 mm Hg, respectively.