Noninvasive evaluation of cardiac function in hypothyroidism. Response to gradual thyroxine replacement

Audit of results of operations for infantile pyloric stenosis in a district general hospital

Because of the proposal that infants with hypertrophic pyloric stenosis should only be treated by surgeons with an interest in paediatric surgery, we carried out a retrospective study to audit our experience in a district general hospital. Forty six infants over a five year period underwent pyloromyotomy. There were no deaths, and 36 infants (78%) made uneventful recoveries. Perforation of the duodenal mucosa occurred during the operation in 11 patients, and eight complications developed in six of these infants. There were seven wound infections, and two patients had vomiting that lasted four days or longer after their operations. There were no long term feeding problems. The results of this study show that such patients can be successfully treated in district general hospitals, and three areas merit special attention: meticulous surgical technique, the use of prophylactic antibiotics, and early graduated feeding.

Thyroid hormone and the cardiovascular system

To understand the pathophysiology of thyroid heart disease, it is necessary to recognize that thyroid hormone has effects on both the peripheral circulation and the myocardium. One of the earliest responses to thyroid hormone administration is a decline in systemic vascular resistance and an increase in cardiac output and cardiac contractility. In many ways, this response is similar to the cardiovascular response to exercise and is associated with increased left ventricular work. The majority of cardiac adaptations to changes in thyroid function are physiologic; however, certain patients do demonstrate clinical evidence of cardiac disease. Atrial arrhythmias, limitations in exercise tolerance, and congestive heart failure are reported to occur as a result of hyperthyroidism and are more common in older patients. Thyroid hormone also plays an important role in the regulation of blood pressure. Diastolic hypertension is a common accompaniment of hypothyroidism. By understanding the mechanisms by which thyroid hormone affects both the peripheral circulation as well as the myocardium, it is possible to predict the clinical response to the treatment of various thyroid disease states.

Effect of thyroid replacement therapy on the frequency of benign atrial and ventricular arrhythmias

Whether thyroid replacement therapy can trigger cardiac arrhythmias in patients with hypothyroidism is not known. In this prospective study, 24 h ambulatory electrocardiographic (ECG) monitoring was used to assess the frequency of atrial and ventricular premature beats in 25 patients with hypothyroidism (5 men and 20 women, aged 56 +/- 3 years) before and 3.5 +/- 0.5 months (mean +/- SEM) after thyroid replacement therapy. Plasma thyroid-stimulating hormone was 73.6 +/- 12.3 and 3.1 +/- 0.6 microU/ml and free thyroxine index was 2.4 +/- 0.4 and 9.8 +/- 0.9 micrograms/100 ml at baseline and after thyroid replacement therapy, respectively. The frequency of ventricular premature beats was not affected by thyroid replacement therapy (from 273 +/- 221 at baseline to 352 +/- 235 beats/24 h after therapy), even in patients with frequent baseline arrhythmias. In contrast, the frequency of atrial premature beats was slightly increased after thyroid replacement therapy (from 47 +/- 17 to 279 +/- 197 beats/24 h), largely as a result of changes seen in three patients. No patient developed new onset of sustained ventricular or supraventricular arrhythmias. Average, basal and maximal heart rates during ECG monitoring increased significantly after thyroid replacement therapy (average 72 +/- 2 to 80 +/- 2; basal 64 +/- 2 to 70 +/- 2; maximal 114 +/- 3 to 130 +/- 3 beats/min, respectively, p less than 0.001). In conclusion, thyroid replacement therapy is safe in patients with common benign cardiac arrhythmias, and does not trigger an increase in arrhythmia frequency except in rare patients with baseline atrial premature beats. It is, however, associated with an increase in basal, average and maximal heart rates.

Left ventricular function at rest and during exercise in acute hypothyroidism

The effect of hypothyroidism on left ventricular function at rest and during exercise was studied in nine patients without demonstrable cardiovascular disease who had had total thyroidectomy and ablative radioiodine treatment for thyroid cancer. Radionuclide ventriculography and simultaneous right heart catheterisation were performed while the patients were hypothyroid two weeks after stopping triiodothyronine treatment (to permit routine screening for metastases) and while they were euthyroid on thyroxine replacement treatment. When the patients were hypothyroid, cardiac output, stroke volume, and end diastolic volume at rest were all lower and peripheral resistance was higher than when they were euthyroid. Pulmonary capillary wedge pressure, right atrial pressure, heart rate, left ventricular ejection fraction, and the systolic pressure:volume relation of the left ventricle, which was used as an estimate of the contractile state, were not significantly different when the patients were hypothyroid or euthyroid. During exercise, heart rate, cardiac output, end diastolic volume, and stroke volume were higher when the patients were euthyroid than when they were hypothyroid. Again, pulmonary capillary wedge pressure, ejection fraction, and the systolic pressure:volume relation were similar in both thyroid states. The data suggest that the alterations in cardiac performance seen in short term hypothyroidism are primarily related to changes in loading conditions and exercise heart rate; they do not suggest that acute thyroid hormone deficiency has a major effect on the contractile properties of the myocardium.

Influence of L-thyroxine on cardiac function in athyreotic thyroid cancer patients--an echophonocardiographic study

We have assessed left ventricular performance in twelve athyreotic patients by echophonocardiography during and after their follow-up investigations. Patients were investigated after 4 weeks without and after 2 as well as 4 weeks of therapy with 150-200 micrograms L-thyroxine (L-T4). At the end of 4 weeks withdrawal of L-T4 patients were severely hypothyroid in terms of T4 and thyrotropin (TSH) serum levels as well as total cholesterol plasma levels. In comparison to values obtained in 12 age and sex matched normal controls left ventricular preejection period was prolonged at that time point (110 +/- 20 vs. 90 +/- 20 (SD) ms, p less than 0.05) and the isovolumetric relaxation period (IVRP) was significantly lengthened (78 +/- 16 vs 54 +/- 10 ms, p less than 0.01). Left ventricular ejection phase indices (fractional shortening and mean velocity of circumferential fiber shortening) did not differ significantly from normal. Preejection period dropped to 90 +/- 20 ms (p less than 0.05) after 4 weeks of therapy with L-T4. IVRP decreased to 67 +/- 13 ms (p less than 0.01) but remained significantly prolonged compared to normal. Serum T4, TSH and plasma cholesterol were compatible with borderline hyperthyroidism at that thime point. Thus, systolic as well as diastolic left ventricular performance (especially during isovolumic phases) appear to respond rapidly to thyroid hormone deficiency of short duration and at least partly to resupplementation.

A double-blind cross-over 12-month study of L-thyroxine treatment of women with 'subclinical' hypothyroidism

Twenty women, who had been randomly selected from women with subclinical hypothyroidism identified in a population study were treated with L-thyroxine and placebo in a double-blind cross-over design during 2 x 6 months. Three women did not complete the study, one because she moved to another part of the country, and two because of nervousness and sense of tachycardia. None of these 'drop-outs' had any objective signs of overtreatment; they had normal pulse rate and a serum T3 concentration within the reference interval. During L-thyroxine treatment serum procollagen-III-peptide concentration increased in 13 women out of the 17 women completing the study and at the end of treatment the mean concentration was significantly raised (P less than 0.001). Serum concentrations of procollagen-III-peptide then correlated with those of free thyroxine (P less than 0.01), total thyroxine (P less than 0.05), and reverse triiodothyronine (P less than 0.05). The same comparison revealed little or no effect on the concentrations of serum creatine kinase activity, transcortin or sex-hormone binding globulin. Heart rate-corrected preejection period and symptom score decreased (P less than 0.05). Four women starting with L-thyroxine showed a marked and prolonged (4-6 months) rise in thyrotrophin concentration during the subsequent placebo period, but remained clinically euthyroid. Four women (of 17) improved during therapy as judged by psychometric testing and their own rating. We could not by pretreatment observations identify these four women apart from serum free and total 3,5,3'-triiodothyronine concentrations in the lower part of the health-associated reference interval. Subclinical hypothyroidism is common among middle-aged and old women, and our findings indicate that approximately one woman in four with this 'subclinical' condition will benefit from L-thyroxine treatment.

Fine adjustment of thyroxine replacement dosage: comparison of the thyrotrophin releasing hormone test using a sensitive thyrotrophin assay with measurement of free thyroid hormones and clinical assessment

Thyroxine replacement therapy for 21 adult patients with primary hypothyroidism was adjusted to the dosage at which each patient had a normal thyrotrophin (TSH) response to thyrotrophin releasing hormone (TRH). Clinical assessment and measurement of TSH (by sensitive immunoradiometric assay), free thyroxine (FT4) and free tri-iodothyronine (FT3) were made at this dosage and at higher and lower doses of thyroxine. Clinical observations, FT3 and FT4 assays were relatively insensitive to small alterations of thyroxine dosage, in contrast to which basal TSH measurements correlated well with TRH responsiveness and were sensitive to fine adjustments of thyroxine dosage.

Hypothyroid cardiomyopathy: echocardiographic documentation of reversibility

The concept of hypothyroid heart disease remains controversial. Although hemodynamic abnormalities have been described, the presence of underlying abnormal cardiac structures has not been confirmed. The authors studied 20 hypothyroid patients using M-mode echocardiography before and after l-thyroxine therapy. Fifteen additional hypothyroid patients were studied using two-dimensional echocardiography to confirm the data of the first study. The findings were the same in both studies: during hypothyroidism, the interventricular septum is thickened, the ratio of septal thickness to left ventricular posterior wall thickening is increased, the right ventricular wall is thickened, regional wall motion of interventricular septum and right ventricular wall is decreased, and global function of the left ventricle is decreased. These findings are reversed with l-thyroxine therapy; they occur within 6 months of the development of hypothyroidism, but appear unrelated to elevated TSH levels. Whether the thickened interventricular septum and right ventricular wall represent true muscular hypertrophy requires further elucidation. Nevertheless, these data demonstrate the existence of a hypothyroid cardiomyopathy.

Late cardiac, thyroid, and pulmonary sequelae of mantle radiotherapy for Hodgkin's disease

Cardiac, thyroid and pulmonary function were evaluated in 25 patients aged 35 years or under, treated for Hodgkin's disease by mantle radiotherapy 5-16 years previously. No patient had symptoms of heart disease. Although thallium myocardial perfusion scintigraphy was normal in all patients, abnormalities of myocardial function were detected in 6 (24%) patients using gated equilibrium rest and exercise radionuclide ventriculography. Resting left ventricular ejection fraction (LVEF) was abnormal in 1 patient, and in 3 patients there was an abnormal LVEF response to exercise. All 6 patients had right ventricular dilatation. Apical hypokinesia was present in 4 of these patients. A small asymptomatic pericardial effusion was detected by M-Mode echocardiography in only 2 (8%) patients. Twenty-three (92%) patients had evidence of abnormal thyroid function. Two (8%) patients had become clinically hypothyroid. Serum TSH was elevated in 13 (52%) patients and TRH stimulation test was abnormal in a further 10 (40%) patients in whom TSH was normal. Pulmonary function studies showed a moderate decrease in diffusing capacity (72% of predicted) and a minor reduction in lung volume. Although a high incidence of cardiac, thyroid and pulmonary abnormalities was detected, only the 2 patients who had become hypothyroid were symptomatic. Modification of the irradiation technique may reduce the incidence of cardiac abnormalities, but is unlikely to alter significantly the thyroid or pulmonary sequelae.

Asymmetric septal hypertrophy and hypothyroidism in children

Any echocardiographic study of two children with hypothyroidism demonstrated the presence of asymmetric septal hypertrophy. One child died aged 11 months, and pronounced thickening of the interventricular septum was confirmed at necropsy. There was also hypertrophy of the left ventricular free wall. Histological examination showed only slight muscle fibre disarray, but there was striking vacuolation and hypertrophy of muscle fibres. In the second case, a child aged five years, the asymmetric septal hypertrophy disappeared after 18 months' treatment with L-thyroxine. Furthermore, other indices of myocardial function also returned to normal. The mechanism producing asymmetric septal hypertrophy in hypothyroidism is unknown. These are the youngest cases in which this association has been reported.

End-organ responses to thyroxine therapy in subclinical hypothyroidism

We studied variables known to change with thyroid hormone status in 18 patients with subclinical hypothyroidism before and during treatment with thyroxine in a dose sufficient to restore the plasma TSH response to TRH to normal. There was an associated increase in both plasma total T4 and free T4 within the normal range but plasma total T3 and free T3 were unchanged. As a result of thyroxine treatment there was a small but significant increase (P less than 0.05) in left ventricular ejection fraction (LVEF) with maximal exercise but no significant changes in LVEF at rest and moderate exercise, continuously monitored mean sleeping heart rate, day/night ratios of urinary sodium excretion, peripheral nerve conduction velocities, fasting serum triglycerides, total cholesterol (TC), high density lipoproteins (HDL) or TC/HDL ratios. On this evidence we do not consider that thyroxine replacement therapy is indicated in patients with subclinical hypothyroidism.

Complications of surgery in hypothyroid patients

Hypothyroidism has generally been considered a contraindication to surgery. To determine the actual risks of perioperative complications in hypothyroid patients, the clinical courses of 40 hypothyroid surgical patients (serum thyroxine concentration 1.9 +/- 1.0 micrograms/dl) were retrospectively compared with those of 80 control patients matched for age, sex, and operative procedure. The two study groups were comparable in preoperative anesthetic physical class, prevalence of other medical conditions, and year of operation. During noncardiac surgery, intraoperative hypotension was encountered more frequently in the hypothyroid patients than in the control patients (61 versus 30 percent, p less than 0.05). Cardiac surgery was complicated by heart failure more often in the hypothyroid patients (29 versus 6 percent, p less than 0.05). Postoperatively, the hypothyroid patients more commonly had gastrointestinal (19 versus 1 percent, p less than 0.02) and neuropsychiatric (38 versus 18 percent, p less than 0.02) complications than control patients. Despite comparable rates of perioperative infection (38 versus 33 percent, p = NS), the hypothyroid patients less frequently manifested fever (35 versus 79 percent, p less than 0.001). There were no differences in perioperative blood loss, duration of hospitalization, or the prevalences of perioperative arrhythmia, hypothermia, hyponatremia, delayed anesthetic recovery, abnormal tissue integrity, impaired wound healing, pulmonary complications, or death. Preoperative clinical and chemical features of hypothyroidism were not useful in defining a subgroup of patients at special risk. Thus, surgery in hypothyroid patients is associated with an increased risk of several minor perioperative complications, which should be anticipated and preemptively managed in the course of their anesthetic and surgical care.

Congenital goitrous hypothyroidism: discordant systolic time intervals, pituitary and peripheral responses to high daily doses of T4 or T3 therapy

Left ventricular performance was studied by a noninvasive technique through the measurement of the systolic time intervals (total eletromechanical systole, left ventricular ejection (LVET) time, preejection period (PEP) and PEP/LVET ratio (Systolic Quotient) in 8 young adults with congenital goitrous hypothyroidism. All subjects showed lengthening of PEP, shortening of LVET and an increased PEP/LVET ratio associated with low serum T3 and T4, an exaggerated TSH response to TRH, high levels of serum cholesterol, triglycerides and carotene. They were treated with increasing L-T4 at monthly intervals (100, 200 and 400 micrograms daily), followed by L-T3 (50 and 200 micrograms daily) after stopping medication for another month. Systolic time intervals and the systolic quotient promptly reversed to the normal range with physiologic L-T4 (100 micrograms) or L-T3 (50 micrograms) replacement, but the TSH peak response to TRH was still present and exaggerated. Further reductions of the systolic quotient occurred with 200 micrograms L-T4, but not with supraphysiological doses (400 micrograms L-T4 or 200 micrograms L-T3) of thyroid hormones. The highest dose of L-T3 (200 micrograms/day) induced a significantly lower mean systolic quotient than 400 micrograms L-T4 daily, while 5 patients still had a significant TSH response to TRH. This was interpreted as discordant pituitary and cardiac response to L-T3 and L-T4 therapy. Serum cholesterol and triglycerides were considered as very sensitive index of thyroid hormone peripheral action. These had a significant positive correlation with changes in the left ventricular performance. Serum carotene, although decreasing significantly with L-T4 or L-T3 treatment, had no significant correlation with the systolic quotient.(ABSTRACT TRUNCATED AT 250 WORDS)

[Myxedema coma. Apropos of 8 cases]

Eight cases of hypothyroid coma observed between 1971 and 1981 are reported, and their main clinical, biological and therapeutic features described. Three out of the 8 patients died. Physiopathological and therapeutic comments are made with reference to these cases and previous reports, concerning the hypothermia, cardiac and respiratory function, hyponatraemia and the endocrine disturbances observed in hypothyroid coma.

The cardiovascular response at rest and during exercise in hypothyroid subjects to thyroxine substitution

Rapid and intense thyroxine substitution can lead to heart failure and myocardial infarction in hypothyroid patients. We have analyzed the normalization of the circulatory system in hypothyroid subjects on a gradual thyroxine substitution. Fourteen hypothyroid patients were studied repeatedly with an orthostatic test and a standardized symptom-limited exercise test during substitution. ST and T abnormalities were observed in 51 and 33%, respectively, before substitution. Many of these changes were normalized upon substitution at a dose level of 0.15 mg/d thyroxine. The pulse reaction to standing was enhanced early during substitution. The capacity to perform work, on the other hand, responded more slowly to thyroxine substitution, and was significantly increased only after six months of full substitution. This difference in the time course of recovery may be of clinical importance when substituting patients with hypothyroidism and ischemic heart disease.

Adaptation to hypocaloric feeding: physiologic significance of the fall in serum T3 as measured by the pulse wave arrival time (QKd)

We have investigated the physiologic significance of the decline in serum triiodothyronine (T3) occurring during hypocaloric feeding by measurement of changes in cardiovascular function. The QKd interval, the interval between the Q wave of the electrocardiogram and the onset of Korotkoff sounds at diastolic pressure at the brachial artery, is the sum of the preejection period and pulsetransmission time, and has proven to be a sensitive and effective measure of the effect of thyroid hormones on the cardiovascular system. Fifteen euthyroid obese volunteers underwent successive 2 wk periods of hypocaloric feeding (200-400 calories per day) interspersed with periods of at least 2 wk of re-feeding on a weight-maintaining diet (1500 calories). In a later phase subjects received oral supplementation of triiodothyronine (T3) in addition to the diet to prevent the fall in serum T3. In the last study phase, subjects on the diet received supplementation with oral thyroxine (T4), which prevented the fall in serum T3 and resulted in a slight increase in serum T4. During the first 2 wk period of hypocaloric feeding, there was a statistically significant increase in QKd, and a decrease in pulse rate, compatible with a hypothyroid state relative to initial measurements. When oral T3 supplementation was given, the rise in QKd and fall in pulse rate were prevented. Likewise, with oral T4 supplementation, the changes in QKd and pulse were prevented. Thus, the fall in serum T3 occurring during hypocaloric feeding is associated with changes in the cardiovascular system which are qualitatively similar to those observed during hypothyroidism. The present data, taken with other data in the literature, suggest that the decline in serum T3 during hypocaloric feeding may be an adaptive mechanism to conserve energy during caloric deprivation.

Early peripheral responses to intravenous L-thyroxine in primary hypothyroidism

The metabolic, cardiovascular, renal, and pulmonary responses of 10 hypothyroid patients were studied during the first week of therapy with intravenous levothyroxine (L-thyroxine), 100 micrograms per day. Mean serum thyroxine, triiodothyronine, and reverse triiodothyronine concentrations were normalized within four days. Significant decreases in serum thyrotropin, creatine phosphokinase, and cholesterol levels, and an increase in the basal metabolic rate, were observed. An early cardiovascular response was demonstrated by serial measurement of the mean pre-ejection period (138 to 134 msec, p less than 0.05), its ratio to left ventricular ejection time (0.49 to 0.46, p less than 0.02), and pulse-wave arrival time (236 to 224 msec, p less than 0.05). The mean renal excretion of a water load (four hours) increased (54 to 77 percent, p less than 0.02) by the fourth day. The blunted ventilatory responses to hypercapnea seen in two patients were improved. We conclude that a physiologic replacement dose of intravenous L-thyroxine for one week produces significant responses in organ systems responsible for the common clinical complications of myxedema.

Left ventricular function in hypothyroidism. Responses to exercise and beta adrenoceptor blockade

The effects of exercise and beta adrenoceptor blockade on left ventricular function were assessed in eight patients with hypothyroidism before and during thyroxine replacement treatment. Left ventricular ejection fraction, measured by radionuclide ventriculography, was reduced in hypothyroid patients at rest and on exercise. The rise in ejection fraction with exercise was, however, similar in both groups. Pretreatment with intravenous propranolol reduced the ejection fraction at rest 9% in both hypothyroid and euthyroid patients and reduced the rise on exercise. Directional changes in a second index of myocardial contractility based on the shape of the ventricular volume curve paralleled the changes in the ejection fraction. Left ventricular function is therefore reversibly depressed by thyroid hormone deficiency but responses to exercise and beta adrenoceptor blockade are normal. There is no evidence of altered adrenergic sensitivity in the control of myocardial contractility in hypothyroidism.

Prolonged persistence of a large pericardial effusion and hemodynamic evidence of cardiac tamponade during treatment of myxedema

We describe clinical, echocardiographic, and catheterization findings that were present initially and during therapy in a myxedematous patient with a large pericardial effusion and tamponade. Treatment with thyroxine resulted in a marked improvement of most of the clinical features of hypothyroidism and some improvement in cardiac function. However, the pericardial effusion as well as clinical and laboratory evidence of tamponade persisted for 2 months after full replacement doses of T4 had been achieved. The tamponade was finally relieved by fenestration of the parietal pericardium. These findings are consistent with evidence of an abnormality of pericardial drainage that persists for months after other thyroid hormone dependent functions are normalized by thyroxine replacement. Therefore prompt surgical drainage rather than dependence on medical therapy alone is indicated in myxedematous patients who have cardiac tamponade.

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.

Cardiac function in mild and severe primary hypothyroidism

One hundred patients with mild to severe primary hypothyroidism have been analyzed for abnormalities in left ventricular performance utilizing noninvasive techniques. These studies have revealed significant abnormalities in cardiac function which correlated inversely with serum T4 levels. The abnormalities in cardiac function were completely reversible with thyroid hormone therapy. Even in patients with mild subclinical hypothyroidism, significant changes in left ventricular performance were achieved by doses of thyroid hormone which normalized TSH secretion. Therapy with either L-T4 or L-T3 resulted in normal cardiac function though L-T3 produced normal cardiac function on lower doses than were necessary to normalize TSH secretion. These studies are intended to provide new information on the optimal treatment of hypothyroidism.

The influence of day and night work on the circadian variations of cardiovascular performance

Circadian variations of the pre-ejection period, Q-T interval, heart rate and oral temperature at rest and in day and night shift work were investigated. At rest, pronounced circadian variation was found in heart rate, pre-ejection period and Q-T interval. The ratio between Q-T interval and heart rate also shows a distinct circadian variation. When working, the rest rhythms of the variables were obscured. The physiological implications for shift work are discussed.

The diminished cardiac performance in severe thyrotoxicosis. Parabolic correlation of LVET/PEP to the circulating levels of thyroid hormones

Fifteen patients with thyrotoxicosis, 8 patients with primary hypothyroidism and 15 normal subjects were studied to assess the correlation between systolic time intervals and serum levels of thyroid hormones. In hypothyroid patients, prolongation of PEPc (corrected pre-ejection period), shortening of LVETc (corrected left ventricular ejection time) and low values of LVET/PEP ratio and cardiac output were improved after restoration of thyroid function. In thyrotoxic patients, shortening of PEPc, high values of LVET/PEP ratio and cardiac output were normalized after correction of thyroid function. As contrasted with these observations, in 5 severely thyrotoxic patients, low values of LVET/PEP ratio and cardiac output for thyrotoxicosis were observed; these were not significantly decreased after antithyroid drug treatment, but appeared to have a tendency to increase. Performing polynomial regression analysis, a significant parabolic correlation was found between LVET/PEP and serum T4 or T3 (p less than 0.0001). From these results, it might be concluded that large amounts of thyroid hormones suppress cardiac performance.

Effects of thyroid hormone on left ventricular function in patients treated for thyrotoxicosis

Systolic time intervals, echocardiographic indexes of left ventricular contractile function and serum triiodothyronine and thyroxine levels were measured before treatment in nine patients with hyperthyroidism, and again every 2 weeks for the first 2 months after therapy and then every 4 weeks until the subjects were clinically and chemically euthyroid. Six of the nine became transiently hypothyroid. Although the preejection period corrected for heart rate (preejection period index) increased as the patients became euthyroid, the change was not significant. Preejection period index increased dramatically in the patients becoming hypothyroid (p less than 0.005). Corrected left ventricular ejection time (left ventricular ejection time index) also increased as the patients became euthyroid (p less than 0.001), and increased again with the appearance of hypothyroidism (p less than 0.05). There was a linear correlation between velocity of circumferential fiber shortening and serum triiodothyronine level (r - 0.77) and between velocity of circumferential fiber shortening and serum thyroxine level (r = 0.70) at all stages of thyroid function. Thus thyroid hormone definitely enhances left ventricular function in human beings, and both excess and deficiency cause predictable reversible changes in myocardial contractile function. Thus thyroid hormone definitely enhances left ventricular function in human beings, and both excess and deficiency cause predictable reversible changes in myocardial contractile function. Furthermore echocardiographic measurements of velocity of circumferential fiber shortening provide rapid estimates of the chemical status of thyrotoxic patients before and after treatment.

Therapy of primary hypothyroidism with L-triiodothyronine: discordant cardiac and pituitary responses

Cardiac systolic time intervals were studied in ten patients with primary hypothyroidism before and during therapy with increasing doses of oral L-triiodothyronine (L-T3). Therapy was increased sequentially from 10, 20, 25 to 50 microgram of L-T3 daily on a monthly basis. On L-T3, 20 to 25 microgram/day, cardiac systolic time intervals and other peripheral responses to thyroid hormone including serum cholesterol concentration, serum creatine phosphokinase (CPK) activity, and basal metabolic rate had normalized. However, serum thyrotrophin (TSH) levels and peak TSH responses to thyrotrophin-releasing hormone (TRH) remained elevated on these doses of L-T3. As the dose of L-T3 was increased from 20 to 50 microgram/day, mean basal serum TSH levels decreased from 55 to 16 microunits/ml, and the peak TSH response to TRH decreased from 243 to 58 microunits/ml (P less than 0.001) while systolic time intervals did not decrease further. Changing to L-thyroxine (L-T4) therapy at this point resulted in further suppression of TSH secretion, without significantly altering systolic time intervals or the other peripheral responses to thyroid hormone. These data suggest (a) that some biological responses to thyroid hormone were normalized on lower doses of L-T3 than were required to normalize TSH secretion, and (b) that higher doses of L-T3 or substituting L-T4 therapy could suppress TSH secretion further without altering the other peripheral responses to thyroid hormone.

Pericardial effusion in hypothyroidism

Thirty-nine patients with untreated hypothyroidism have been examined using echocardiography for the presence of a pericardial effusion. Effusions were present in twelve patients who tended to be more severely hypothyroid. Plasma creatine phosphokinase and lactate dehydrogenase levels were higher in the presence of an effusion. Nine were reinvestigated during thyroxine replacement therapy and the effusions did not disappear until thyroid function tests had returned to normal. There were no specific electrocardiographic changes associated with the presence of an effusion which could be associated with a normal cardiac silhouette on a standard P.A. chest X-ray.

Echocardiographic characterization of the reversible cardiomyopathy of hypothyroidism

Nineteen patients with untreated hypothyroidism were evaluated by M-mode echocardiography. Asymmetric septal hypertrophy (ASH), defined as a ratio of interventricular septal thickness to left ventricular posterior wall thickness (IVS/LVPW) equal to or greater than 1.3, was identified in 17 cases. Additional abnormalities recognized by echocardiography included reduced amplitude of systolic septal excursion (SSex) [13 patients], reduced per cent of systolic septal thickening (%SST)[19 patients], reduced left ventricular outflow tract dimension (LVOT)[five patients] and systolic anterior motion of the mitral valve (SAM)[five patients]. These findings are similar to some of the echocardiographic features of idiopathic hypertrophic subaortic stenosis (IHSS). In 10 patients who returned to euthyroid state with L-thyroxine therapy, these abnormalities resolved. We conclude that long-standing hypothyroidism leads to a reversible cardiomyopathy, manifested by asymmetric septal hypertrophy with or without other echocardiographic features of a hypertrophic obstructive cardiomyopathy. This previously unrecognized features of hypothyroidism has important diagnostic and therapeutic implications.

Systolic time intervals: a valuable parameter of thyroid function

Conventional systolic time interval measurements were made in 49 patients presenting with hypertyroidism, euthyroidism, or hypothyroidism. A linear correlation was observed over the entire range of thyroid function ( r = 0.75) between Δ PEP and the serum free T4 index. A linear correlation was also found between the PEP/LVET ratio and the serum free T4 index ( r = 0.70). A higher correlation was found between the PEP/LVET ratio and the serum free T4 index when plotted logarithmically ( r = 0.75).

During treatment of hyperthyroidism, the PEP progressively lengthens and the PEP/LVET ratio increases, whereas during treatment of hypothyroidism the PEP shortens progressively to normal values while the PEP/LVET ratio diminishes.

In amiodarone-induced hyperthyroidism, both a prolonged PEP and an increased PEP/LVET ratio were found. These controversial measurements, suggesting a diminished cardiac contractility, may be explained by a worsened cardiac ischemia due to the development of hyperthyroidism.

Systolic time interval measurements appear to be a valuable tool in the assessment of the cardiac response to thyroid hormone during both hypothyroidism and hyperthyroidism.

Preoperative endocrine and metabolic considerations

Patients with endocrine dysfunction have an increased risk of intraoperative and postoperative morbidity. Identification of such patients prior to surgery, and preoperative management to achieve normal hormonal status may prevent or lessen episodes of morbidity. Diabetics undergoing elective surgical procedures can be managed by any number of approaches. Whatever the method used, close monitoring of blood glucose levels is imperative.

Idiopathic oedema: a study of the effects of bromocriptine

We have studied the effect of bromocriptine in seven patients with idiopathic oedema. Two patients were unable to tolerate the drug; the remaining five were maintained on doses of between 5 and 7.5 mg a day. Symptomatic improvement was noted in two patients and in both of these and one other there was a significant improvement in mean diurnal weight gain. The fall in free water and sodium clearance on standing was reduced by bromocriptine, but there was no significant change in the excessive fall in plasma volume.