Author + information
- Paolo Angelini, MD∗ ()
- ↵∗Department of Cardiology, Texas Heart Institute, 6624 Fannin, Suite 2780, Houston, Texas 77030
The recent review by Corban et al. (1) highlights the limitations of the literature on myocardial bridges (MBs) and suggests the need for clearly defined terms and protocols. For example, to clearly establish the prevalence of MB, clinical identification should require 2 angiographic views obtained after nitroglycerin administration, rather than computed tomography (whose use should probably be limited to measuring length and depth). Chest pain, myocardial infarction, and sudden death are not systematically associated with MB of any anatomic severity; most MBs are benign. As Corban et al. (1) note, MBs actually prevent coronary artery disease (CAD) inside affected segments. Statements regarding pathophysiology, clinical indications, and adverse effects in MB require clearly defined inclusion and exclusion criteria (symptomatic or asymptomatic MB vs. MB with associated comorbidities that may influence clinical presentation, e.g., hypertrophic cardiomyopathy). To determine the cause of sporadic ischemic symptoms, workup must first rule out significant CAD; worsening of systolic, phasic arterial narrowing at MB sites (by dobutamine testing and angiography); and, especially, spasticity or endothelial dysfunction (by acetylcholine testing) (2–4).
Subselective intraluminal devices (e.g., pressure or Doppler wires, intravascular ultrasound catheters) should be generally avoided outside of experimental protocols because they can alter MB by inducing spasm and deforming the affected coronary segment (2,3). Incidentally, the “half-moon” sign associated with MB probably results from the fiberoptic probe bending at the MB site; it is not a true marker of MB severity (only of its presence).
Although fractional flow reserve has been advocated (1,2) as a measure of MB clinical severity and the prognosis of associated CAD, this measurement does not reveal the hemodynamic severity of MB, nor does it reflect prognosis, as it can in moderate atherosclerotic lesions. Definitive study of MB will require large, controlled, prospective, multicenter investigations with long-term, objective clinical follow-up. Anything less will only perpetuate the current state of confusion and uncertainty about this entity.
- American College of Cardiology Foundation