abstract & commentary
Synopsis: Dilated coronopathy is characterized by nonobstructive coronary artery flow reductions and myocardial ischemia. Also, nitroglycerin is of no therapeutic benefit.
Source: Kruger D, et al. J Am Coll Cardiol 1999;34: 1461-1470.
An occasional patient with exertional angina or myocardial infarction (MI) will have coronary artery ectasia or aneurysm (CEA) formation on coronary angiography without significant stenosis. Why do these patients have myocardial ischemia is the question asked by Kruger and colleagues. Among 16,341 patients undergoing cardiac catheterization between 1986 and 1997 in two university hospitals in Germany, 507 with CEA were identified (3%). Saccular aneurysms were found in 14, unilateral fusiform aneurysms in 39, and 387 had CEA with significant coronary stenoses. These 440 patients were excluded, leaving the study population of 67 patients with bilateral fusiform CEA without significant stenoses or dilated coronopathy. Of the 67 patients, 25 had MI and 11 of these had occlusion of the infarct-related artery. Further studies were done on the 42 patients without prior infarction. Typical exertional angina was present in 37 of these 42, and five had atypical symptoms severe enough to warrant catheterization. Pacing stress coronary sinus lactate studies documented myocardial ischemia in 32 of the 42 patients (reduced lactate extraction), and exercise ECG testing was positive for ischemia in 29. These results were markedly different from a control group of 29 patients with a similar risk profile but no heart disease. Nitroglycerin markedly accentuated the ischemic response to pacing with 32 of 42 patients developing lactate production. Coronary artery luminal diameters were strongly related to the severity and extent of ischemia (r = 0.87; P < 0.001) and stigmata of impaired coronary blood flow, such as delayed antegrade filling, segmental back flow, and local dye deposition (P < 0.04). Kruger et al conclude that dilated coronopathy is characterized by nonobstructive coronary artery flow reductions and myocardial ischemia. Also, nitroglycerin is of no therapeutic benefit in this entity.
Comment by Michael H. Crawford, MD
The angiographic literature suggests an incidence of CEA ranging from 0.3-4.9%, so the 3% incidence in this study is believable and agrees with my experience. This study clearly showed that CEA without significant stenoses can be a cause of myocardial ischemia (about 75% incidence in this study). Also, this study shows that MI can occur in patients with CEA (33% incidence in this study). In addition, Kruger et al demonstrated that exercise-induced ischemia can be found in the majority of symptomatic patients with nonobstructive CEA. Finally, Kruger et al showed evidence of reduced coronary blood flow in nonobstructive CEA patients with symptoms. Thus, the clinical presentation of nonobstructive CEA is similar to garden variety coronary atherosclerosis and this specific diagnosis must be made with coronary artery imaging or direct inspection.
The etiology of CEA is not completely clear. Perhaps half the cases or more are associated with atherosclerosis, 20-30% may be congenital, and 10-20% are of inflammatory origin (vasculitis). In this series of middle-aged adults (mean age, 53 years) without evidence of inflammatory diseases, most probably had coronary atherosclerosis. Why do some patients with atherosclerosis develop CEA? This answer is unknown, but some theories have been advanced. One is that CEA represents post-stenotic dilatation. This could be, but doesn’t explain the frequent occurrence of prestenotic lesions. Histologic studies show an increase in the intimal layer with thinning of the media in atherosclerotic cases and loss of media in nonatherosclerotic cases, suggesting that loss of the media is a common pathway to CEA. Why some patients with atherosclerosis lose media and develop CEA is unknown, but could be genetic. Also, some have suggested that this is a compensatory mechanism to try to open the lumen of the vessel.
The mechanism of myocardial ischemia in non-obstructive CEA is also unclear. The reduction in epicardial coronary artery blood flow observed could simply be a result of vessel dilatation by Poiseuille’s law or may be due to impaired microvascular flow. The latter could be caused by microemboli from the aneurysmal areas. Thus, our usual armamentarium for coronary disease is largely appropriate for these patients. Unstable angina and MI should be treated in the usual way with the caveat that IV nitroglycerin may be ineffective or even harmful. In the chronic patient, platelet inhibition seems particularly important, but the role of warfarin is unclear. Some would argue that chronic warfarin could be important to reduce microemboli or frank coronary occlusion due to flow stasis in these aneurysmal vessels, but there is no evidence to support its use or nonuse. Beta-blocker therapy seems reasonable, especially in symptomatic patients since this study showed pacing-induced ischemia. However, since nitrates were ineffective, what about calcium blockers? They also dilate coronary arteries and could be as ineffective as nitrates, but there are no data on this topic. In general, therapy of patients with dilated coronaropathy should be individualized to the particular situation with attention to the issue that coronary vasodilatating drugs may not be effective. (Dr. Crawford is Robert S. Flinn Professor, Chief of Cardiology, University of New Mexico, Albuquerque.)
Coronary ectasia and aneurysms are associated with:
a. myocardial ischemia.
b. Marfan syndrome.
c. hereditary telangectasia.
d. None of the above