The effect of myxedema on the cardiovascular system

Ventricular septal perforation following acute myocardial infarction in a patient with hypothyroidism--a case report

A 61-year-old woman with profound hypothyroidism underwent surgery for a ventricular septal perforation 15 days following an acute myocardial infarction, with no preoperative thyroid replacement. Her immediate postoperative course was complicated by a low cardiac output, respiratory suppression and high output renal failure, requiring prolonged hemodynamic and respiratory support. Thyroid replacement (50 micrograms of thyronine and 100 micrograms of thyroxine daily) was given in two installments on the 2nd day after the operation. The effect of the inotropic agents increased gradually and the patient was weaned off intra-aortic balloon pumping. A large quantity of diuretics, hydration and hyperalimentation also successfully reduced her elevated BUN and serum creatinine. After full thyroid replacement, she was discharged in good health on the 40th postoperative day.

Hormonal and nutritional enhancement of Na+-K+-ATPase activity may aid the prevention and treatment of essential hypertension

Subnormal activity of the Na+-K+-ATPase appears to be a common feature of essential hypertension, and may in fact play a pathogenic role in this disorder. If so, methods which relieve inhibition or enhance the activity of the sodium pump should have therapeutic or preventive value. Diuretics enhance the activity of the sodium pump in hypertensives, apparently by suppressing secretion of an inhibitory natriuretic factor, and it is likely that low-sodium diets have a similar effect. Activity of the Na+-K+-ATPase is also stimulated by thyroid hormone and insulin, and there are indications that thyroid therapy, as well as various measures which increase tissue insulin sensitivity, may have therapeutic value in essential hypertension. Nutritional measures which may enhance sodium pump activity include potassium supplementation, insurance of adequate magnesium intake, and consumption of rich sources of gamma-linolenic acid.

Cardiac dimensions and myocardial function of infants with congenital hypothyroidism. An echocardiographic study

This study was undertaken to evaluate the cardiac dimensions and various indices of myocardial function, determined by echocardiography, in a group of 12 infants with congenital hypothyroidism. Left ventricular systolic and diastolic dimensions, posterior wall thickness, enddiastolic and systolic volumes were all significantly lower in the hypothyroid infants compared with 25 normal infants of the same age. No pericardial effusion was found. Hypothyroid infant had a lower heart rate with a reduced cardiac output. The mean velocity of circumferential fibre shortening and the shortening fraction of the left ventricle were normal. The pre-ejection period of the left ventricle (PEP), however, was abnormally prolonged as well as the ratio PEP over left ventricular ejection time (PEP/ET). This ratio correlated inversely with the end-diastolic volume, suggesting that the increased PEP/ET could be partly the result of decreased preload.

Compromise therapy in the patient with angina pectoris and hypothyroidism. A clinical assessment

The teaching that thyroid replacement therapy can aggravate angina or induce myocardial infarction in patients with hypothyroidism and coronary disease, and thus compel acceptance of incomplete control of either, was substantiated in 51 patients (18 with iatrogenic and 30 with idiopathic primary hypothyroidism, and three with secondary hypothyroidism as a component of panhypopituitarism). Based upon clinical and laboratory criteria, control of hypothyroidism was unsatisfactory in two fifths of the patients. Judged by frequency and ease of induction of angina and nitroglycerine requirement, control of angina was unsatisfactory in one-third. In many patients maximal tolerated dose of thyroid varied with time. The effect of combined propranolol and thyroid therapy in 13 patients was quite satisfactory in seven patients, fair in three and poor in three, but excellent in none. Transfusions were useful as a short- or long-term expedient in a few. Of 12 patients considered for coronary revascularization, three were rejected because of other medical problems and one showed prompt improvement after the dose of thyroid was decreased. Five of the remaining eight studied by coronary cineangiography were rejected as unsuitable for surgery. The remaining three were subjected to coronary revascularization. One did well for a time, apparently until a graft became occluded, the remaining two are still doing well. Coronary bypass graft surgery may deserve a larger role in the future management of these patients.

Re-evaluation of a possible high incidence of hypertension in hypothyroid patients

In an attempt to re-evaluate a possible high incidence of hypertension in hypothyroid patients, blood pressure was measured in 38 slightly hypothyroid patients, in 17 moderate hypothyroid patients, and in 26 severe hypothyroid patients. The data were then compared with the findings in 73 known euthyroid subjects and in 1,601 possibly euthyroid subjects. Blood pressure and incidence of hypertension increased progressively with age in known euthyroid subjects and in possibly euthyroid subjects. Similarly, blood pressure increased progressively with age in slight and moderate hypothyroid patients, but the incidence of hypertension was high in the sixth decade in slightly hypothyroid patients for some unknown reason. In contrast, blood pressure and the incidence of hypertension were low in the fifth and sixth decades in severe hypothyroid patients. This low blood pressure was elevated slightly when Sv1 + Rv5 and C/T were shifted toward normal by T4 treatment for 3 to 4 months. It is suggested that the hypothyroid state does not accelerate the development of hypertension.

Influence of the thyroid state on left ventricular tension-velocity relations in the intact, sedated dog

The mechanical properties of left ventricular contraction were described in terms of tension, velocity, length, and time in closed-chest, sedated normal, hypothyroid, and hyperthyroid dogs. Heart rate was controlled at 150 beats/min, and instantaneous contractile element velocity was calculated from left ventricular pressure and its first derivative during isovolumic left ventricular contractions, produced by sudden balloon occlusion of the ascending aorta during diastole. Wall tension was derived from ventricular pressure and volume, the latter being obtained from the pressure-volume relation of the arrested ventricle, and tension-velocity relations were analyzed over a range of ventricular endiastolic volumes. At any level of ventricular volume, the hypothyroid state was associated with a displacement of the tension-velocity relation of the left ventricle downwards and to the left, and the time to peak tension was prolonged (154 msec, normal 139 msec). In the hyperthyroid state, the tension-velocity relation of the left ventricle was displaced upwards and to the right, and the time to peak tension was reduced (80 msec). The changes in the tension-velocity relations indicate that the inotropic state of the left ventricle in the intact dog varies directly with the animal's thyroid state. This influence on myocardial contractility necessarily constitutes an important and integral part of the response of the intact circulation to altered thyroid state.

Changes in the electrocardiogram and achilles reflex test during treatment of hypothyroidism

In 10 patients with hypothyroidism, the electrocardiogram and Achilles reflex test have been recorded before and during treatment with l-thyroxine sodium. Aspects of the electrocardiogram affected by hypothyroidism are the rate, duration of PR interval, height of P-wave, of QRS complex and of T-wave and the ST segment. Each of these improved with therapy, the earliest and most sensitive change being the height of the QRS complex. The Achilles reflex time as recorded by the photomotograph also showed a parallel decrease with therapy but this is considered to be less reliable as an isolated test. The prolongation of the PR interval is briefly discussed and a correlation between the changes in skeletal and myocardial muscle is suggested.

Serum lactic dehydrogenase isoenzymes in "myxoedema heart disease"

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