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When mapping premature ventricular contractions (PVCs) originating from around the right ventricular outflow tract (RVOT) or left ventricular outflow tract (LVOT), insulated myocardial pathway conduction that is connected to an exit to the ventricular myocardium is sometimes observed.1, 2 Insulated myocardial pathways are usually detected as discrete or fractionated prepotentials preceding the QRS onset during PVCs, but sometimes they are detected as late potentials during sinus rhythm (SR).3, 4, 5 Although the existence of insulated myocardial pathways has been reported,1, 2, 3, 4, 5, 6 the electrophysiological and anatomic characteristics of the insulated myocardial pathways have not been fully clarified. Here we present the case of a PVC with an insulated myocardial pathway for which the detailed electrophysiological and anatomic characteristics were evident.

Introduction Diagnostic criteria for coronary microvascular spasm (CMS) have not yet been fully established. Case presentation We present two cases of CMS in which decreased coronary blood flow velocities were observed during acetylcholine (ACH) provocation tests. The first patient suffered from chest pain occurring while at rest. The patient underwent coronary angiography (CAG), which revealed a decrease in the average peak velocity (APV) from 29 cm/s to 14 cm/s and a slow flow phenomenon following ACH injection. The second patient suffered from chest pain occurring during the night. The patient underwent CAG, which revealed a decrease in the APV from 17 cm/s to 7 cm/s with no significant epicardial coronary artery spasm following ACH injection. Both patients complained of chest pain, and electrocardiogram changes were observed in leads equivalent to the distal area of the vessel during an ACH provocation test. These findings were consistent with CMS, and their conditions improved under medical treatment. Discussion A transient decrease in coronary blood flow velocity following ACH administration might be a phenomenon specific to CMS. These cases may provide some insight into the underlying pathophysiology of CMS.