ELECTROCARDIOGRAPHIC STUDIES, INCLUDING WORK TEST AND GANGLIONIC BLOCK

Abstract

SummaryThe ECG recorded from unipolar leads has been studied in 49 cases of Friedreich's ataxia. A work test on the bicycle ergometer was performed by 36 patients, in the wheel‐chair cases by cranking. The ECG changes in the standing position and after sympathetic ganglionic blocking have also been studied. The following observations are made:1. Sinus tachycardia is present at rest in one‐third of the cases, and the heart rate is unusually high in the standing position.2. Supraventricular and ventricular extrasystoles are most common in groups III and IV. In a few cases, sudden bradycardia occurs immediately after work, as a result of disturbance of the atrial impulses. Atrial fibrillation and paroxysmal supraventricular tachycardia are found to occur in the late stages of the disease.3. Signs of left ventricular hypertrophy are most common in groups I and II, and of right ventricular hypertrophy in groups III and IV. High voltage of the It waves is common and sometimes extremely pronounced. The development of signs of hypertrophy has been studied.4. Right axis deviation of QRS is present in more than half of the patients in group IV. Only one patient has left axis deviation.5. Abnormal Q waves are not recorded. The Q–T duration is normal, with no difference between the groups.6. The most usual ECG change is T wave inversion. In about two‐thirds of the cases, the T wave is negative in one or more of leads I, II, aVF and V7.7. The affected members of a family often show a similar pattern of ECG changes. Only 3 patients have a normal ECG at rest.8. At rest in the standing position, inverted T waves become positive in one‐third of the cases. During and after exercise, this T wave reversion is seen in 24 of 31 cases. It is suggested that this normalization is to be ascribed to a sympathetic effect on myocardial fibrosis, as may occur after myocardial infarction.9. Ganglionic blocking has been used to study the ECG reaction. A definite tendency to normalization of inverted T waves is noted in 6 of 16 tested cases. This may be due to the action of vasodilatation on myocardial metabolism and nutrition.10. In 21 cases, the ECG recordings have been followed up during an observation period ranging from 4 to 17 years. T wave inversion is found to occur at an early stage, but subsequently remains unchanged in 13 of the cases. In 6 cases there is successive reversion of the T wave.