The relationship between intermittent left bundle-branch block and slow coronary flow in a patient presenting with acute coronary syndrome.

Coronary slow flow phenomenon (CSFP) is characterized by delayed opacification of coronary vessels in a normal coronary angiogram. The incidence of CSFP is reportedly 1% among patients undergoing coronary angiography, and is more prevalent in patients presenting with acute coronary syndromes (ACS). Over 80% of patients with CSFP experience recurrent chest pain. A relationship between CSFP and ventricular arrhythmias has also been reported. Left bundle-branch block (LBBB) is a strong, independent predictor of heart failure, sudden cardiac death, cardiovascular death, and all-cause death. New onset LBBB has also been shown to be prognostic for patients with ACS, and should be considered in risk stratification to identify high-risk patients. We report intermittent LBBB associated with CSFP in a patient presenting with ACS. We propose that LBBB may be a result of coronary ischemia secondary to CSFP in left anterior descending coronary artery and that intermittent LBBB may have a prognostic role for detecting coronary ischemia.