Mitsuru Nagata

Exercise-induced systolic dysfunction in patients with non-obstructive hypertrophic cardiomyopathy and mutations in the cardiac troponin genes

Objectives: The aim of this study was to investigate left ventricular (LV) function reserve in hypertrophic cardiomyopathy (HCM) patients with and without cardiac troponin gene mutations before transition to the dilated phase. Methods: LV ejection fraction (EF) was continuously evaluated in 52 patients with non-obstructive HCM during supine ergometer exercise using radionuclide ventricular function monitoring with a cadmium telluride detector (VEST). On the basis of genetic analysis, patients were divided into two groups: 10 with cardiac troponin gene mutations (group A) and 42 without these gene mutations (group B). Results: Exercise duration, peak exercise load, and heart rate during exercise did not differ between the two groups. The differences from baseline to peak exercise of the LV end-diastolic volume decreased similarly in the two groups. In contrast, the difference of the LV end-systolic volume in group A increased significantly compared with group B (17.7% (SD 12.7%) vs 3.4% (SD 13.2%); p = 0.0031). Consequently, the difference of LVEF in group A decreased significantly in contrast with group B (–14.1% (SD 11.1%) vs –1.2% (SD 11.7%); p = 0.0025). Additionally, the changes in LVEF and stroke volume decreased significantly more in group A than in group B (–22.2% (SD 18.6%) vs –1.1% (SD 17.8%); p = 0.0017 and –12.9% (SD 21.7%) vs 12.3% (SD 24.4%); p = 0.0042, respectively). Conclusions: These results suggest that HCM patients with cardiac troponin gene mutations may display exercise-induced LV systolic dysfunction more frequently than HCM patients without this abnormality.

Pilsicainide intoxication presenting as left ventricular dyssynchrony in a patient on hemodialysis

We report here a case of pilsicainide intoxication presenting as left ventricular dyssynchrony in a patient who had been treated on hemodialysis. This is the first report that assessed cardiac function during pilsicainide intoxication by left ventriculography and right heart catheterization.

Coronary arteriovenous fistulas complicated by complete atrioventricular block: A case report

We report the case of a patient with bilateral coronary arteriovenous fistulas (CAVFs) connecting the right coronary artery and left circumflex coronary artery with the right atrium who had progression of first-degree atrioventricular (AV) block to complete AV block during a 4-year period. The His bundle electrogram revealed that the complete AV block was the result of a block at the level of the AV node. Dipyridamole stress thallium-201 myocardial imaging showed decreased perfusion in the inferoapical wall. Coronary angiography and computed tomography showed fistulas that arose from the AV nodal branch of the right coronary artery and from the distal portion of the circumflex coronary artery and drained into the right atrium. Because the fistulas were small, they were not repaired surgically, and a permanent pacemaker was implanted to treat the complete AV block. We presumed that the complication by complete AV block was due to abnormalities of the arteries feeding the AV node and chronic ischemia resulting from a coronary steal associated with the fistulas. To the best of our knowledge, this is the first report of CAVF complicated by complete AV block.

A case of left ventricular diverticulum: Change of characteristics after myocardial infarction and usefulness of cardiac computed tomography

A 72-year-old man with an old myocardial infarction was admitted to our hospital for cardiac reexamination. He had suffered from an inferior myocardial infarction when he was 60-year-old. The left ventriculogram had then shown a small contractile diverticulum at the apical portion of the left ventricle. Anterior myocardial infarction had recurred when he was 63-year-old. The left ventriculogram performed after the anterior myocardial infarction revealed that the diverticulum had become dilated and non-contractile. On admission, electrocardiography and chest X-ray showed no remarkable changes from the previous studies. Cardiac computed tomography (CT) demonstrated an apical left ventricular diverticulum with narrow communication to the main chamber and myocardial discontinuity of the wall at the site of the diverticulum. Tc-99m tetrofosmin myocardial images showed a perfusion defect in the apex. We presumed that a muscular left ventricular diverticulum had changed to the fibrous type after the anterior myocardial infarction. Cardiac CT imaging provides accurate evaluation of the left ventricular diverticulum and is useful for the differentiation between a left ventricular diverticulum and an aneurysm.