Silent myocardial ischemia: Therapeutic implications

doi:10.1016/0002-9343(85)90491-7

The American Journal of Medicine

Volume 79, Issue 3, Supplement 1, 13 September 1985, Pages 30-34

https://doi.org/10.1016/0002-9343(85)90491-7 Get rights and content

Abstract

Current concepts concerning the pathophysiology of acute myocardial ischemia are reviewed. The importance of intermittent, dynamic shifts in the diameter of the coronary artery lumen is emphasized. Traditionally, it has been thought that angina pectoris is the common clinical hallmark of myocardial ischemia. It is now apparent that asymptomatic episodes of myocardial ischemia may be occurring far more frequently than symptomatic episodes. Although the natural history of asymptomatic myocardial ischemia is still unknown, ischemia, even in an asymptomatic form, can have serious consequences. This suggests the need for a careful assessment of patients in whom ischemia has been detected. In truly asymptomatic patients, detection is usually fortuitous; in patients with known coronary arterial disease, asymptomatic episodes should be sought as part of a noninvasive cardiac investigation, using multiple-stage exercise treadmill testing and 24-hour ambulatory electrocardiographic monitoring. Suggestions are made for the management of asymptomatic myocardial ischemia in relation to three patient groups: (1) asymptomatic ischemia in patients known to have symptomatic ischemia as well, (2) asymptomatic ischemia in patients without symptoms at anytime, and (3) asymptomatic ischemia in patients who have had myocardial infarction. Medical management includes the use of calcium channel blocking drugs, betaadrenergic blocking drugs, and nitrates. Documentation of an inadequate coronary artery reserve or evidence of associated left main coronary artery disease indicates the need for either aortocoronary bypass graft surgery or percutaneous transluminal coronary angioplasty, depending on the condition of the coronary anatomy and the degree of ventricular function. Whatever mode of treatment is used, documentation of its effectiveness should always be determined by appropriate follow-up studies. Clinical studies of the natural history of asymptomatic myocardial ischemia and its management are urgently needed.

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Citation Excerpt :
There are several reports of the therapeutic efficacy of antianginal agents in reducing both angina pectoris and episodes of silent ischemia (29,30). Medical management traditionally consists of calcium channel blockers, beta-blockers, and nitrates (31). However, there are limited data to suggest that improvement of ischemia with these medications, as detected by ambulatory Holter monitoring, results in more favorable clinical outcomes.
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1990, The American Journal of Cardiology
Current noninvasive diagnostic techniques have limited accuracy for detection of coronary artery disease (CAD) in symptomatic and (particularly) asymptomatic patients with silent disease. Furthermore, no standard noninvasive method provides reliable diagnostic information on the location of the coronary arteries involved, the severity of stenosis, the presence of collaterals and myocardial viability. Based on 1,000 cardiac studies at the University of Texas, cardiac positron emission tomography (PET) with either generator-produced rubidium-82, cyclotron-produced N-13 ammonia, or F-18 deoxy-glucose is suitable for 4 routine diagnostic purposes: (1) noninvasive diagnosis of CAD in either symptomatic or asymptomatic subjects with a sensitivity of 95 to 98% and specificity of 95 to 100%. This accuracy is now sufficient to schedule diagnostic catheterization and multivessel angioplasty with surgical backup on the basis of the PET scan. At the University of Texas we carry out PET in asymptomatic and symptomatic patients to direct those with mild disease to cholesterol-lowering reversal therapy and those with severe disease to percutaneous transluminal coronary angioplasty (PTCA); (2) assessment of physiologic severity of coronary artery stenosis as compared to automated quantitative coronary arteriographic analysis. Changes in stenosis severity are followed before and after interventions including PTCA, bypass surgery, vasodilator drugs and cholesterol control regimens for reversal of coronary atherosclerosis; (3) imaging myocardial infarction, ischemia, viability, zone at risk and sizing of these pathophysiologic processes. Major therapeutic decisions such as cardiac catheterization, bypass surgery and PTCA are made on the basis of the PET scan alone when clinical and catheter information are not definitive; and (4) identification and assessment of significant collateral function in humans by imaging myocardial steal after intravenous dipyridamole.
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Although thillium exercise imaging has served an important role in clinical cardiology, it is significantly limited by suboptimal sensitivity and specificity, particularly in asymptomatic man. The increasing recognition of silent myocardial ischemia, the significant prevalence of coronary artery disease in asymptomatic middle age men, and the frequent occurrence of myocardial infarction without preceding symptoms in 60% of cases emphasizes the need for a more definitive, noninvasive diagnostic test for the presence of coronary artery disease suitable for screening in asymptomatic or symptomatic patients. Intravenous dipyridamole comvined with handgrip stress provides a potent stimulus for purposes of diagnostic perfusion imaging. Although planar and single photon emission computed tomography (SPECT) imaging also have played an important role, these techniques are seriously hindered by their inability to quantitate radiotracer uptake or image modest differences in maximum relative flow caused by coronary artery stenosis. Accordingly, the combination of dipyridamole-handgrip stress with positron imaging of myocardial perfusion has become a powerful diagnostic tool suitable for routine clinical use. With the availability of generator-produced rubidium-82, dedicated clinically oriented positron cameras, the routine application of positron imaging to clinical cardiology has become feasible. Based on published literature, the current clinical indications for positron imaging that may be carried out economically on a routine clinical basis include (a) assessment of myocardial perfusion utilizing rubidium-82 or N-13 ammonia for purposes of reliable, accurate, noninvasive screening for coronary artery disease in symptomatic or asymptomatic patients; (b) assessing noninvasively the physiologic severity of coronary stenoses; (c) myocardial infarct imaging; (d) assessing myocardial viability of reversibly injured or ischemic cells using N-13 ammonia combined with fluorine-18-deoxy-glucose or Rubidium-82 alone in experimental animals; (e) assessing regional or global left ventricle (LV) function by 3-dimensional gated blood pool imaging and/or wall thickening by ECG gating; and (f) assessing the functional significance of collaterals in man.
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Silent myocardial ischemia: Therapeutic implications

Abstract

Am J Cardiol

Am Heart J

Am J Cardiol

Am J Cardiol

J Am Coll Cardiol

Lancet

Lancet

Am Heart J

Am J Cardiol

Am Heart J

The Lumleian lectures on angina pectoris

Lancet

Coronary artery spasm

N Engl J Med