Alterations in the transmural gradient of ventricular repolarization with different pacing sites in normal and heart failure canines.

Alterations of the transmural gradient of repolarization may contribute to the increase of transmural dispersion of repolarization and ventricular arrhythmias. The transmural gradient of repolarization may play an important role in sudden death associated with left ventricular epicardial pacing. To investigate the changes of transmural gradient dispersion of ventricular repolarization with different pacing sites in heart failure (HF) canines, 8 mongrel dogs were randomized into healthy group and HF group (n = 4). We mapped the monophasic action potential duration (MAPD) in the subendocardial, subepicardial and mid-myocardial layers of the left ventricle (LV) in canines of healthy and HF groups during right atrium (RA) pacing, right ventricular apical endocardial (RVEndo) pacing, left ventricular lateral epicardial (LVEpi) pacing and biventricular (Biv) pacing respectively. The results showed that in the healthy group, the MAPDs were significantly different among the three layers during RA pacing (all P < 0.05). The MAPD was longer in the mid-myocardial layer compared with those in the subepicardial and subendocardial layers during RVEndo, LVEpi or Biv pacing (P < 0.05). However, there was no significant difference in MAPD between the subendocardial and subepicardial layers during RVEndo, LVEpi or Biv pacing (P > 0.05). In the HF group, the MAPDs in all three layers were prolonged compared with those in the same locations in the healthy group (all P < 0.05). However, there were no differences in MAPD among the three layers during RA, RVEndo, LVEpi or Biv pacing (all P > 0.05). By MAP recording with our new mapping electrode, we found a transmural MAPD gradient among the three layers of the LV during RA pacing and the gradient between the subendocardial and subepicardial layers vanished during RVEndo, LVEpi or Biv pacing in healthy dogs. In contrast, there was no transmural MAPD gradient during RA, RVEndo, LVEpi or Biv pacing in HF dogs. These results are helpful to understand the mechanism of ventricular arrhythmias in patients with HF.

Ventricular Tachycardia and Resembling Acute Coronary Syndrome During Pheochromocytoma Crisis: A Case Report.

Pheochromocytomas are neuroendocrine tumors, and its cardiac involvement may include transient myocardial dysfunction, acute coronary syndrome (ACS), and even ventricular arrhythmias.A patient was referred for evaluation of stuttering chest pain, and his electrocardiogram showed T-wave inversion over leads V1 to V4. Coronary angiography showed 90% stenosis in the mid-left anterior descending coronary artery (LAD), which was stented. Five days later, the patient had ventricular tachycardia, and severe hypertension, remarkable blood pressure fluctuation between 224/76 and 70/50 mm Hg. The patient felt abdominal pain and his abdominal ultrasound showed suspicious right adrenal gland tumor. Enhanced computed tomography of adrenal gland conformed that there was a tumor in right adrenal gland accompanied by an upset level of aldosterone.The tumor was removed by laparoscope, and the pathological examination showed pheochromocytoma. After the surgery, the blood pressure turned normal gradually. There was no T-wave inversion in lead V1-V4. Our case illustrates a rare pheochromocytoma presentation with a VT and resembling ACS. In our case, the serious stenosis in the mid of LAD could be explained by worsen the clinical course of myocardial ischemia or severe coronary vasospasm by the excessive amounts of catecholamines released from the tumor. Coronary vasospasm was possible because he had no classic coronary risk factors (e.g. family history and smoking habit, essential hypertension, hyperglycemia and abnormal serum lipoprotein, high body mass index). Thus, pheochromocytoma was missed until he revealed the association of his symptoms with abdominalgia.As phaeochromocytomas that present with cardiovascular complications can be fatal, it is necessary to screen for the disease when patients present with symptoms indicating catecholamine excess.