Ventricular fibrillation induced by transesophageal atrial pacing in hypertrophic cardiomyopathy

Sudden death is a rather frequent occurrence in patients withhypertrophic cardiomyopathy, yet the mechanism is uncertainin most cases. We describe a case of an 18 years old patientwith a family history of hypertrophic cardiomyopathy and suddendeath in whom ventricular fibrillation could be repeatedly inducedby means of transesophageal atrial stimulation with 1 : 1 AVconduction at a rate of 200 beats min^-1 and prevented by pharmacologicaldepression of AV node. The not particularly high ventricularrate at which VF occurred could suggest that in hypertrophiccardiomyopathy a major role in favouring VF induction is playedby the electro-physiological properties of the myocardium andthat sudden death can occur as a consequence of different atrialtachyarrhythmias.     

High doses of L-carnitine in acute myocardial infarction: metabolic and antiarrhythmic effects

Fatty acids accumulate in the muscle cells in some carnitinedeficiency syndromes due to a variety of genetic defects inintermediary metabolism. L-Carnitine administration may relievethis excess by transporting acyl compounds out of the cell asacylcarnitine. Similar fatty acid accumulation occurs duringmyocardial ischae-mia because of the decreased rate of fi-oxidation,and this has been put forward as a cause of ventricular arrhythmias.This study was carried out to investigate whether administrationof high doses of i.v. L-carnitine in patients with acute myocardialinfarction could increase urinary excretion of acylcarnitineand reduce early ventricular arrhythmias. Fifty-six patients suffering from acute myocardial infarction,admitted to the Coronary Unit between 3 and 12 h after the onsetof symptoms, were included in the study. The design of the study was double blind, parallel and placebocontrolled. Allocation of treatment to patients was done randomlyafter stratification (time from onset of pain and site of infarction).The first group (28 patients) received intravenous L-carnitineat a dose of 100 mg kg^–1 b.w. every 12 h for 36 h whilethe second group (28 patients) received placebo intravenously.Immediately before starting treatment two blood samples weretaken (at 5-min intervals) and a further 16 samples were takenat regular intervals over the following 48 h. Patients' urinewas collected over the same period of time. Concentrations offree carnitine, short chain acylcarnitine esters and long chainacylcarnitine esters in serum and urine were measured. On days1 and 2, 24-h ECG monitoring (Holler) was carried out. Analysis of results showed that: (1) in patients receiving placebo,free carnitine serum levels increased significantly during thefirst 48 h after infarction; (2) in the same group of patients,free and total urinary carnitine excretion was significantlyhigher than in normal subjects; (3) administration of high dosesof L-carnitine considerably increased urinary excretion of longand short chain carnitine esters; (4) this metabolic effectmight explain the reduction in premature ventricular beats onthe second day of treatment.     

Doppler echocardiographic assessment of time to peak velocity in the aorta and pulmonary artery of small for gestational age fetuses

Summary. The time to peak velocity was measured at the level of the ascending aorta and pulmonary artery by Doppler echocardiography in 38 small-for-gestational age (SGA) fetuses before and during maternal hyperoxygenation. The values were compared to a reference range derived from the study of 142 appropriate-for-gestational age (AGA) fetuses. In the SGA fetuses the time to peak velocity at the level of pulmonary artery was significantly lower and at the level of the aorta significantly higher than in AGA fetuses. During maternal hyperoxygenation the aortic time to peak velocity decreased towards normal range but there was no significant change at the level of the pulmonary artery. These results may indicate variations of aortic and pulmonary pressures in SGA fetuses that can be partially modified by maternal hyperoxygenation and which may be associated with changes in the peripheral resistance of the cerebral circulation.