Echocardiographic characterization of the reversible cardiomyopathy of hypothyroidism

Hypothyroid cardiomyopathy: A reversible phenocopy of hypertrophic cardiomyopathy

We present the case of a 46-year-old patient with hypothyroidism secondary to Hashimoto's thyroiditis who was admitted with decompensation in the form of myxedema. A 2-D echocardiogram shows a septal asymmetric hypertrophy, with low-voltage QRS complex in the ECG and a bull's-eye map of longitudinal strain with preserved apical strain with reduction of mid and basal strain that results in "cherry on the top" pattern, similar to the most frequent phenocopy of hypertrophic cardiomyopathy, as is the cardiac amyloidosis, and that, unlike this pathology, reverted after the patient reached the euthyroid state.

Thyroid hormone levels within reference range are associated with heart rate, cardiac structure, and function in middle-aged men and women

BACKGROUND

Triiodothyronine (T3) has many effects on the heart, and marked changes in cardiac function and structure occur in patients with (subclinical) thyroid disease. We investigated whether between-subject variation in thyroid hormone levels within the euthyroid range is also associated with heart rate and echocardiographic heart function and structure.

METHODS

Subjects were selected from the Asklepios study (n=2524), a population-representative random sample of patients aged between 35 and 55 years, free from overt cardiovascular disease at baseline. Analyses were restricted to 2078 subjects (1013 women and 1065 men), not using antihypertensive or thyroid medication nor having antithyroperoxidase antibody levels above clinical cut-off or thyrotropin (TSH) levels outside the reference range. All subjects were phenotyped in-depth and underwent comprehensive echocardiography, including diastolic evaluation. Thyroid function parameters were determined by automated electrochemiluminescence.

RESULTS

Heart rate was robustly positively associated with (quartiles of) free T3 (FT3) and T3, both in subjects with TSH levels within reference (0.27-4.2 μU/L) and in narrow TSH range (0.5-2.5 μU/L; p<0.0001). FT3 and T3 were negatively associated with left ventricular (LV) end-diastolic volume but positively associated with relative wall thickness. Total T3 (TT3) was associated with enhanced ventricular contraction (as assessed by tissue Doppler imaging). Free thyroxine, FT3, and TT3 were positively associated with late ventricular filling, and TT3 was associated with early ventricular filling.

CONCLUSION

We have demonstrated a strong positive association between thyroid hormone levels within the euthyroid range and heart rate, and more subtle effects on cardiac function and structure. More specifically, we suggest a smaller LV cavity size (with increased relative wall thickness), an enhanced atrial and ventricular contraction, and LV relaxation with higher circulating thyroid hormones. These results illustrate that variation in thyroid hormone levels, even within the reference range, exerts effects on the heart.

Safety of obesity drugs

The safety of obesity drugs has historically been poor. This and the stigmatisation of obesity in society ensured that a higher standard of safety for obesity drugs must be met. The authors review the safety disasters of obesity drugs that were withdrawn. The authors then review the safety of presently available drugs--benzphetamine, phendimetrazine, diethylpropion, phentermine, sibutramine and orlistat. The safety of rimonabant, a drug with a pending new drug application that has an independent effect on metabolic syndrome, is also reviewed. The authors compare the stage of obesity drug development to that of hypertension in the 1950s. As new and safer drugs with more downstream mechanisms are developed that have independent effects on the cardiovascular risks associated with obesity, third party reimbursement for obesity medicine is likely to improve. This may lead to obesity being treated like hypertension and other chronic diseases with long-term medication. With improved technological tools, the authors believe this process will be more rapid for obesity than it was for hypertension.

Répercussions cardiaques des dysthyroïdies avérées

KEY POINTS

Thyroid hormones affect the vascular system, including the diastolic and systolic functioning of the heart. Resting heart rate increases early in hyperthyroidism (cardiac contractility expands due to improved ventricular loading and decreased systemic vascular resistance). Paradoxically, these hemodynamic alterations progressively reduce cardiac performance on effort (changes in diastolic, then systolic functioning) and finally at rest (modification in ventricular loading following tachycardia or atrial fibrillation), especially in cases of underlying heart disease (in the elderly). Hypothyroidism has an inverse hemodynamic effect and is less noisy, usually limited to relative bradycardia. The morbidity and mortality associated with hypothyroidism are apparently related to the atherogenic and prothrombotic vascular modifications that follow thyroid hormone deficiency, whereas heart failure and particularly atrial fibrillation and its thromboembolic complications are the primary consequences of hyperthyroidism. In both cases, return to normal thyroid levels corrects the cardiac abnormalities caused by the dysthyroidism. Dysthyroidism (hypo- or hyperthyroidism) occurs in 10 to 20% of the patients treated with amiodarone for arrhythmia. Because of its potential seriousness, some clinical or laboratory tests are necessary before initiating treatment, and specific clinical surveillance should be scheduled, including laboratory tests.

[Asymmetric septal hypertrophy associated with "subclinical hypothyroidism"]

We report a case of hypothyroid cardiomyopathy manifested as reversible asymmetric septal hypertrophy in a 61-year-old white woman diagnosed 20 years previously with primary hypothyroidism.

Hypothyroidism as a risk factor for cardiovascular disease

The cardiovascular risk in patients with hypothyroidism is related to an increased risk of functional cardiovascular abnormalities and to an increased risk of atherosclerosis. The pattern of cardiovascular abnormalities is similar in subclinical and overt hypothyroidism, suggesting that a lesser degree of thyroid hormone deficiency may also affect the cardiovascular system. Hypothyroid patients, even those with subclinical hypothyroidism, have impaired endothelial function, normal/depressed systolic function, left ventricular diastolic dysfunction at rest, and systolic and diastolic dysfunction on effort, which may result in poor physical exercise capacity. There is also a tendency to increase diastolic blood pressure as a result of increased systemic vascular resistance. All these abnormalities regress with L-T4 replacement therapy. An increased risk for atherosclerosis is supported by autopsy and epidemiological studies in patients with thyroid hormone deficiency. The "traditional" risk factors are hypertension in conjunction with an atherogenic lipid profile; the latter is more often observed in patients with TSH >10 mU/L. More recently, C-reactive protein, homocysteine, increased arterial stiffness, endothelial dysfunction, and altered coagulation parameters have been recognized as risk factors for atherosclerosis in patients with thyroid hormone deficiency. This constellation of reversible cardiovascular abnormalities in patient with TSH levels <10 mU/L indicate that the benefits of treatment of mild thyroid failure with appropriate doses of L-thyroxine outweigh the risk.

Assessment of left ventricular diastolic function by radionuclide ventriculography at rest and exercise in subclinical hypothyroidism, and its response to L-thyroxine therapy

Hypothyroidism is associated with intrinsic myocardial changes reflected by alterations in contractility and relaxation. Diastolic function, however, rather than systolic cardiac function, seems to be mostly impaired by thyroid hormone deprivation. Our aim was to evaluate diastolic function at rest and during maximal exercise by means of radionuclide ventriculography in subclinical hypothyroidism before and after restoration of euthyroidism. Ten subclinical hypothyroid patients (50 +/- 8.7 years) (thyroid-stimulating hormone 11 +/- 4.2 microUI/ml) without cardiac disease were studied before and 6 months after levothyroxine (L-T(4)) replacement (thyroid-stimulating hormone 1.9 +/- 1.1 microUI/ml). We compared the basal and post-therapy cardiac parameters with a control group of 14 euthyroid patients (52.5 +/- 10 years) (thyroid-stimulating hormone 2.5 +/- 1.2 microUI/ml). Multigated equilibrium radionuclide ventriculography was performed to assess systolic and diastolic ventricular function. Student's t and paired Student's t tests were applied for statistical analysis. We found a significant difference between the time to peak filling rate (TPFR) at rest before (0.241 +/- 0.002 ms) and after (0.190 +/- 0.012 ms) treatment with L-T(4). A significant difference that disappeared after restoration of euthyroidism was also observed between the basal TPFR values of the subclinical hypothyroid patients and the control group (0.189 +/- 0.01 ms). The same pattern was observed at maximal exercise. Thus, TPFR, a parameter of left ventricular (LV) diastolic function measured by radionuclide ventriculography, is impaired in subclinical hypothyroid patients both at rest and during exercise and returns to normal values after L-T(4) therapy.

Insulin resistance and hyperinsulinemia: No independent relation to left ventricular mass in humans

BACKGROUND

Hyperinsulinemia and insulin resistance may contribute to the development of cardiac hypertrophy. In humans, however, the evidence is inconclusive.

METHODS AND RESULTS

We studied 50 nondiabetic subjects covering a wide range of age (20 to 65 years), body mass index (BMI, 19 to 40 kg x m(-2)), and mean blood pressure (72 to 132 mm Hg). Plasma insulin concentrations and secretory rates were measured at baseline and during an oral glucose tolerance test; insulin sensitivity was measured by the insulin clamp technique. Left ventricular mass (LVM) (by 2D M-mode echocardiography) was distributed normally and was higher in obese (BMI >/=27 kg x m(-2), n=16) or hypertensive patients (blood pressure >140/90 mm Hg, n=21) (50+/-8 and 55+/-10 g x m(-2.7), respectively) than in 13 nonobese, normotensive subjects (40+/-8 g x m(-2.7), P:=0.0004). In a multivariate model adjusting for sex, age, BMI, and blood pressure, neither insulin concentrations (fasting or postglucose) nor insulin sensitivity or secretory rates were significant correlates of LVM. Systolic blood pressure (P:=0.003) and BMI (P:=0.01) were the only independent correlates of LVM. From the regression, the impact of hypertension (as a systolic pressure of 180 versus 140 mm Hg=+20%) was twice as large as that of obesity (as a BMI of 35 versus 25 kg x m(-2)=+11%), the two factors being additive.

CONCLUSIONS

When adequate account is taken of body mass and blood pressure, insulin, as concentration, secretion, or action, is not an independent determinant of LVM in nondiabetic subjects.

Molecular characterization of myocardial fibrosis during hypothyroidism: evidence for negative regulation of the pro-alpha1(I) collagen gene expression by thyroid hormone receptor

The purpose of this study was to gain insights into the underlying mechanism of myocardial fibrosis during hypothyroidism. Treatment of cardiac fibroblasts with a medium lacking thyroid hormone led to a 47% increase in [3H]thymidine incorporation into the cell nuclei compared with that in untreated cells. Northern blot analysis of RNA from cardiac fibroblasts grown in a thyroid hormone depleted medium resulted in a 38% increase in the abundance of mRNA for pro-alpha1(I) collagen. At the protein level, the amount of type I collagen, as determined by immunoprecipitation, was increased either in the cell lysate (46%) of cardiac fibroblasts grown in a thyroid hormone depleted medium or in the medium (44%). The chimeric plasmid, ColCAT 3.6, contains the 5'-flanking region of the rat pro-alphal(I) collagen gene (from bases -3520 to +115) fused to the chloramphenicol acetyltransferase (CAT) gene. The plasmid was cotransfected with thyroid hormone receptor (TR) expression plasmid into rat cardiac fibroblasts and COS-l cells (monkey mesangial cells). Cells transfected with the ColCAT plasmid in the presence of thyroid hormone (100 nM T(3)) had a significant decrease (39% in fibroblasts, P<0.01; 52% in COS-1 cells, P<0.001) in CAT activity when compared to cells not exposed to thyroid hormone. Transient co-transfection of TR with various pro-alphal(I) collagen/CAT deletion constructs showed that T(3)-dependent repression was preserved with the deletion from 3520 bp of the flanking sequence to a 5' end point at position -224, indicating that a thyroid hormone-response element (TRE) was localized at the region -224 to +115. The TR-DNA binding assays demonstrated binding of the human TRbeta1 to a fragment containing a proposed TRE located between position -35 and +115 in the 5'-flanking region of the rat pro-alphal(I) collagen gene.

Changes in cardiac function at rest before and after treatment in primary hypothyroidism

The aim of the present study was to investigate in hypothyroid patients the reversibility of the prolongation of electromechanical delay and of the impairment of early diastolic relaxation as measured by radionuclide ventriculography after restoration of euthyroidism. We also evaluated Doppler echocardiography in relation to scintigraphic findings. Twenty-six consecutive hypothyroid patients were studied at diagnosis and after treatment. The time to peak ejection decreased (161 +/- 6 vs 145 +/- 5 ms; p = 0.03) without changes in global systolic function (ejection fraction). The peak filling rate was reversible as well: 2.6 +/- 0.1 versus 3.0 +/- 0.2 end-diastolic volume/s; p = 0.003. No significant changes in systolic and diastolic cardiac function or ventricular geometry were detected by Doppler echocardiography. However, subanalysis of profoundly hypothyroid patients (free T4 < 4.5 pmol/L, n = 8) revealed a decrease in the septal wall thickness (9.9 +/- 0.7 vs 8.3 +/- 0.4 mm, p = 0.01) and increases in early peak transmitral inflow velocity (53 +/- 4 vs 65 +/- 4 cm/s, p = 0.03), as well as left ventricular end-diastolic diameter (4.8 +/- 0.1 vs 5.1 +/- 0.2 cm, p < 0.05) after treatment. Thus, in primary hypothyroidism, a subtle reversible prolongation of contraction without major changes in global systolic function and a decrease in early active relaxation is observed by radionuclide ventriculography. Echocardiography shows changes only in severely hypothyroid patients.

Severe short-term hypothyroidism is not associated with an increased incidence of myocardial ischemia as assessed by thallium-201 stress/rest myocardial scintigraphy

Reversible silent myocardial ischemia associated with treatment of long-standing hypothyroidism has recently been reported using thallium-201 (201Tl) myocardial single photon emission tomography (SPET). The aim of the present study was to evaluate whether patients with short-term hypothyroidism (serum thyrotropin [TSH] levels above 30 mU/L) have an increased risk of silent myocardial ischemia. We studied 20 patients with differentiated thyroid carcinoma that had undergone thyroidectomy and ablative (131)I therapy. None of the patients had a known history of atherosclerotic cardiovascular disease. In the course of a planned follow-up examination, suppressive levothyroxine (LT4) therapy was discontinued 7 weeks prior to scintigraphy and replaced by triiodothyronine (T3) therapy for 4 weeks. No thyroid hormone medication was given during the 3 weeks preceding the diagnostic procedures. All patients were hypothyroid (TSH 87.2 +/- 30.8 mU/L, mean +/- SD) at the time of the examination. 20lTl-SPET was performed immediately after bicycle exercise stress test and again after a delay of 4 hours. In case of abnormal results, (n = 3) the examination was repeated after patients were euthyroid. Two patients showed effects of soft-tissue attenuation (breast attenuation in a female and diaphragmatic attenuation in a male subject). Myocardial ischemia was revealed in 1 patient but was seen in both hypothyroid and euthyroid examinations. The results of the present study show that short-term severe hypothyroidism as encountered in athyreotic patients after cessation of thyroxine medication for several weeks, is not associated with an impairment of myocardial perfusion.

Cardiac systolic and diastolic function at rest and exercise in subclinical hypothyroidism: effect of thyroid hormone therapy

Cardiac atrial and ventricular parameters were determined by Doppler two-dimensional echocardiography at rest and exercise in 8 patients with subclinical hypothyroidism (SCH) (6 women and 2 men; age range: 28-48 years) before and 3 months after achievement of a euthyroid state with incremental adjustment of L-thyroxine therapy. None of the patients had known heart disease. At 3 months of L-thyroxine therapy, TSH levels decreased from 14.8 +/- 9.4 mIU/L to 3.0 +/- 1.5 mIU/L and FTI increased from 7.1 +/- 1.8 to 8.1 +/- 1.9. The cardiac studies were performed at rest, and during incremental exercise load (50, 100, 150 W workload) on a Quinton exercise bicycle. No significant differences were found between the subclinical hypothyroid and euthyroid states in systolic blood pressure at rest (104.8 +/- 12.3 vs 105 +/- 10.1 mm Hg) and exercise (158 +/- 24.9 vs 158.5 +/- 20.9 mm Hg) or diastolic blood pressure at rest (70 +/- 4.7 vs 69 +/- 5.7 mm Hg) and exercise (86 +/- 11.4 vs 89.2 +/- 7.3 mm Hg). All echocardiographic atrial and ventricular parameters were similar before and during L-thyroxine therapy with the exception of a small but significant change in left ventricular diastolic dimension (4.5 +/- 0.3 vs 4.8 +/- 0.4 cm; p < 0.05). All Doppler parameters were not significantly affected by L-thyroxine therapy with the exception of preejection period at stage III exercise (51 +/- 17 vs 39 +/- 13 msec; p < 0.05). Preejection period at other stages of exercise showed trends toward similar differences between subclinical hypothyroidism and euthyroidism, but the differences were not statistically significant. We conclude that the cardiac structure and function overall remains for practical purposes normal in subclinical hypothyroidism. However, the latter may be responsible for a mild prolongation of the preejection period during exercise and a slightly smaller left ventricular diastolic dimension at rest, changes that may not be of clinical significance in patients without underlying heart disease.

Thyroid disease: effects on cardiovascular function

Thyroid hormones exert direct effects upon the heart and indirect influences mediated via changes in cardiac work. Overt thyroid dysfunction is frequently associated with cardiovascular symptoms and signs and less frequently with significant cardiovascular morbidity due to atrial fibrillation or cardiac failure. Whether subclinical thyroid dysfunction is similarly associated with adverse effects upon the cardiovascular system remains unclear.

Restrictive and hypertrophic cardiomyopathies in Noonan syndrome: the overlap syndromes

A woman with Noonan syndrome had clinical and haemodynamic features of restrictive cardiomyopathy. There was no ventricular hypertrophy on echocardiography but myocardial biopsies showed myocyte hypertrophy without pathological disarray. This case illustrates the overlap of the cardiac phenotypes of Noonan syndrome, restrictive cardiomyopathy, and hypertrophic cardiomyopathy.

Silent myocardial ischemia in hypothyroidism

In some patients with severe hypothyroidism thyroxine replacement therapy precipitates or aggravates angina pectoris, whereas in other patients angina pectoris is ameliorated or even disappears. The reason for this paradox is unknown. It has been attributed either to reversible endocrine cardiomyopathy in the form of asymmetric septal hypertrophy (ASH) or reversible anatomical narrowing of the coronary arteries. The results of a recent investigation, in which myocardial performance was surveyed by radionuclide ventriculography throughout early thyroxine replacement therapy in severe hypothyroidism, were compatible with the presence of reversible coronary dysfunction rather than of ASH. The aim of the present investigation was to confirm these findings. In six severely hypothyroid patients, without echocardiographic evidence of ASH or evidence of concomitant coronary artery disease (CAD), exercise and redistribution tomographic myocardial thallium-201 imaging (SPECT) was performed before thyroxine replacement therapy and repeated after 10 days and again after 2 months during therapy. In four patients substantial regional perfusion defects were demonstrated after exercise that were normalized at rest both before, and in one subject also after 10 days, on thyroxine. With restoration of euthyroidism, exercise and redistribution SPECT were normal in every patient. Determination of exact confidence limits reveals that the proportional incidence of myocardial perfusion defects in hypothyroidism, indicating myocardial ischemia, will at least be 22% with 95% probability. Despite the relatively low specificity of SPECT it seems pertinent to conclude that impaired myocardial perfusion as assessed by SPECT probably is due to reversible coronary dysfunction inherent in the hypothyroid state, and that this is not an infrequent manifestation of severe hypothyroidism.

Hospitalized congestive heart failure patients with preserved versus abnormal left ventricular systolic function: clinical characteristics and drug therapy

PURPOSE

To compare clinical characteristics of and pharmacologic therapy for hospitalized patients with congestive heart failure (CHF) and left ventricular systolic dysfunction or normal left ventricular systolic function.

PATIENTS AND METHODS

Medical records were reviewed for all patients discharged with a principal diagnosis of CHF from a university hospital and a community hospital between September 1, 1991 and August 31, 1992. Pertinent medical history items and prescribed drug therapies at discharge were recorded for each patient's first calendar year admission. Patients were categorized as having either normal left ventricular systolic function or systolic dysfunction based on the results of echocardiography and radionuclide angiography or contrast ventriculogram.

RESULTS

Of 298 patients with CHF, 92 (31%) had normal left ventricular systolic function. Patients with normal systolic function were older, were more often women, were less likely to have a history of coronary artery disease, and were more likely to have a history of hypothyroidism than patients with systolic dysfunction. However, the prevalence of clinical characteristics overlapped considerably between the two groups. Among patients with systolic dysfunction, 79% were discharged on a therapeutic regimen of digoxin, 65% on an angiotensin-converting enzyme inhibitor, and 26% on either a beta-blocker or a calcium channel blocker. Among patients with normal systolic function, 50% were discharged on a regimen of a beta-blocker or a calcium channel blocker and 38% were discharged on digoxin. Twenty-six percent of patients with normal systolic function and without a history of atrial fibrillation were discharged on a digoxin regimen.

CONCLUSION

Hospitalized CHF patients with normal left ventricular systolic function and those with diminished left ventricular systolic function share many clinical features. Since recommended drug therapy and prognosis differ, our data underscore the importance of diagnostic testing to assess left ventricular systolic function. Drug therapy for CHF patients provides a major challenge for quality-of-care improvement.

Incidence of hypertrophic cardiomyopathy in hypothyroidism

In 13 consecutive severely hypothyroid patients no sign of endocrine cardiomyopathy in the form of asymmetric septal hypertrophy (ASH) could be disclosed by M-mode and two-dimensional (2D) echocardiography on examination prior to thyroxine replacement therapy. In previous investigations ASH was demonstrated to be almost invariably present in untreated hypothyroidism irrespective of thyrotropin levels. Consequently application of positive inotropic and afterload reducing agents that may invoke deleterious effects in ASH has been considered hazardous in hypothyroidism even when indicated by concurrent other heart disease. Determination of exact confidence limits reveals that the proportional incidence of hypothyroid hypertrophic cardiomyopathy could not exceed 24.7% with 95% probability. We conclude that ASH is not necessarily inherent in hypothyroidism.

Effects of thyroid hormone and thyroid dysfunction on the cardiovascular system

Thyroid disease is common in veterinary practice. The heart, especially the myocardium, is sensitive to thyroid hormone, and deficiencies or excesses can alter cardiovascular function. Observed changes result from direct effects upon the myocardium and indirect effects that result from effects upon the vasculature and peripheral tissues. Clinically significant cardiovascular abnormalities related to hypothyroidism are rare. If present, they are primarily manifest as reduced left ventricular pump function, as apparent echocardiographically, or arrhythmias. Hyperthyroidism is common in the cat and infrequently encountered in dogs. Clinically significant cardiovascular manifestations are common and often dramatic. Hyperdynamic systolic function and mild myocardial hypertrophy are common manifestations which may lead to overt congestive and high output heart failure. If signs of congestive heart failure or significant arrhythmias are not evident, specific therapy need only be directed toward restoration of the euthyroid state. In most cases the cardiovascular changes associated with thyroid dysfunction are completely reversible.

The thyroid and the heart

Cardiovascular manifestations are a frequent finding in hyperthyroid and hypothyroid states. In this review, potential mechanisms by which thyroid hormones may exert their cardiovascular effects and pathophysiological consequences of such effects are briefly discussed. Two major concepts have emerged about how thyroid hormones exert their cardiovascular effects. First, there is increasing evidence that thyroid hormones exert direct effects on the myocardium, which are mediated by stimulation of specific nuclear receptors, which in turn leads to specific mRNAs production. Furthermore, there is some evidence that thyroid hormones may also activate extranuclear sites and may directly alter plasma membrane function. Second, thyroid hormones interact with the sympathetic nervous system by altering responsiveness to sympathetic stimulation presumably by modulating adrenergic receptor function and/or density. Pathophysiological consequences of such direct and indirect thyroid hormone effects include increased myocardial contractility and relaxation that may be related to stimulation by T3 of specific myocardial enzymes. However, when left ventricular hypertrophy occurs in association with hyperthyroidism, it may be related to either direct thyroid hormone-induced stimulation of myocardial protein synthesis or to thyrotoxicosis-induced increases in cardiac work load. Although hyperthyroidism generally has little or no effect on mean arterial blood pressure, hypothyroidism is often associated with increases in diastolic blood pressure that are reversible after hormone substitution and may be mediated in part by sympathetic activation. Moreover, there is increasing evidence that thyroid hormones have direct chronotropic effect on the heart that are independent of the sympathetic nervous system.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation, by noninvasive methods, of the effects of acute loss of thyroid hormones on the heart

To evaluate the effects of the acute loss of thyroid hormones on the heart the authors studied 11 women with acute hypothyroidism. The cardiac study was performed by means of electrocardiography (ECG), radionuclide ventriculography (RNV) at rest and under effort, and monodimensional echocardiography (MD-echo) and was repeated with ECG and MD-echo after six months of thyroxine suppressive therapy. The ECG showed a significant prolongation of QT interval and flattening and inversion of T wave with normal heart rate. The MD-echo revealed left ventricular function in the normal range and normal left ventricular dimensions. RNV showed the ejection fraction in the lower normal range at rest, which increased to a smaller extent under effort in comparison with a control group. The ECG performed during suppressive therapy with L-thyroxine yielded normal findings with an increase of heart rate and of R wave amplitude, and the MD-echo showed no significant variations of cardiac function due to the increase of heart rate.

Cardiac left ventricular function before and during early thyroxine treatment in severe hypothyroidism

In some patients with severe hypothyroidism, thyroxine replacement therapy precipitates or aggravates angina pectoris, whereas in other patients angina pectoris is ameliorated or even cured. Cardiac function in eight severely hypothyroid patients was studied by means of radionuclide ventriculography (RNV) at rest and during supine bicycle exercise before thyroxine treatment, and repeated during treatment before and after administration of 160 mg of oral verapamil. There was an exercise-induced fall in left ventricular ejection fraction (LVEF) in two patients before therapy, and in two additional subjects after 17 d on suboptimal doses of thyroxine. Verapamil attenuated the fall and induced a significant increase in LVEF during exercise (P less than 0.014). No abnormal regional cardiac wall movement (RWM) was observed. After 2 months of thyroxine treatment, LVEF increased significantly during exercise both before and after verapamil (P less than 0.012 and P less than 0.005). These findings are indicative of reversible coronary artery dysfunction. We recommend that, if feasible, thyroxine should be supplemented with verapamil during the early phase of treatment.

The spectrum of echocardiographic abnormalities in hypothyroidism and the effect of hormonal treatment

Cross-sectional echocardiography was used to identify and quantify different cardiac abnormalities in 85 patients with hypothyroidism. Pericardial effusion was the most common and was found in 32 patients (37.6%), while abnormal increase in left ventricular dimensions with impairment of function followed next in frequency (16.4%). Asymmetrical septal hypertrophy as well as segmental wall motion abnormality were each detected in 11.76%. Holosystolic prolapse of the mitral valve was present in only 4.7% of the cases. Different combinations of abnormalities were observed in a total of 22 patients (25.76%), and pericardial effusion was a constant finding. Some of the abnormalities were reversed with physiological thyroxin replacement, but abnormal wall motion remained unimproved.

Cardiomyopathy in children in Ahmedabad

A clinical study and follow up of 20 children with cardiomyopathies upto age of 16 years are presented. The DCM was most common variety followed by RCM and HCM in pediatric age group. SHMD presenting with cardiomyopathy were common in infancy and early childhood. Cardiomyopathies presented most frequently between 2-5 years and 10-16 years age group with DCM having almost equal distribution. Clinical presentation of various types is described, despite of vigorous decongestive and vasodilator treatment in advanced cases, course was rapidly downhill and prognosis is poor in general.

The role of noncardiac disease in the development and precipitation of heart failure

The varying roles of a widely diverse group of noncardiac disorders on the heart, particularly their ability to induce heart failure, are explored. A general overview of the cardiac effects of volume and pressure overloading is followed by specific discussions of the roles of vascular, endocrine and metabolic, renal, gastrointestinal, central nervous system, hematologic, and other miscellaneous disorders (heat stroke, sepsis, immune-mediated disease, obesity, malnutrition, and pregnancy) in producing cardiac dysfunction and failure in companion animals. Pathogenetic and pathophysiologic mechanisms are emphasized.

Cardiac function in congenital hypothyroidism: impairment and response to L-T4 therapy

Electrocardiograms (heart rate, QRS voltage, QRS axis in the frontal plane. Q-Tc interval) echocardiograms [left ventricular fractional shortening (LVFS); preejection period (PEP); PEP/left ventricular ejection time (PEP/LVET) ratio; end-diastolic left ventricular free wall and interventricular septum thickness; presence of pericardial effusion], and thyrotropin (TSH), thyroxine (T4), and triiodothyronine (T3) serum levels were evaluated before and 1 week, 1 and 2 months after the start of L-thyroxine (L-T4) therapy in 11 infants with congenital hypothyroidism (CH), aged 16-59 days when first seen. Before the start of therapy, infants with CH had significantly lower QRS complexes and LVFS and significantly higher values for Q-Tc, PEP, and PEP/LVET than normal infants of the same age. The QTc interval, PEP and PEP/LVET ratio of infants with CH were significantly greater before than 1 week after L-T4 therapy, and LVFS was significantly lower before than 1 month after L-T4 therapy. Four of the infants with CH had small pericardial effusions, which disappeared within the first week of therapy. QRS axis in the frontal plane, Q-Tc interval, and PEP were negatively correlated with logT4 and logT3 serum levels. PEP/LVET ratios were negatively correlated with logT4 serum values. The QRS voltage values were positively correlated with logT4 and logT3 serum values. The frontal-plane QRS axis, Q-Tc interval, and PEP/LVET ratio were positively correlated with logTSH serum levels. The QRS voltages were negatively correlated with TSH serum levels.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

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.

Hypertrophic cardiomyopathy and thyroid diseases

The incidence ratio of thyrotoxicosis among 14 patients with thyroid diseases associated with hypertrophic cardiomyopathy was compared with that in 7686 patients with thyroid diseases, to find the possible correlation between thyrotoxicosis and hypertrophic cardiomyopathy. Thyrotoxicosis did not predominate over other thyroid diseases in the 14 patients with hypertrophic cardiomyopathy. Thus, the occurrence of hypertrophic cardiomyopathy does not appear to be associated with thyrotoxicosis.

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.

Natural history of primary myxedema

It is generally admitted that primary myxedema in adults is the outcome of autoimmune atrophic thyroiditis. The present review traces the natural history of this process from its incipient biologic and genetic anomalies up to its protracted asymptomatic course, clinical development, and eventual lethal complications. The apprehension of preclinical hypothyroidism may change a clinician's outlook on early diagnosis and therapy.

Borderline low thyroid function and thyroid autoimmunity. Risk factors for coronary heart disease?

Assessments were made of 945 consecutive hospital patients with regard to a relation between borderline low thyroid function (recognised by a slightly raised thyroid stimulating hormone), thyroid autoimmunity, serum cholesterol, and coronary heart disease. Men and women with a thyroid autoimmunity, serum cholesterol, and coronary heart disease. Men and women with a thyroid stimulating hormone of 4.0 mU/l or over had a higher prevalence of coronary heart disease than did age-matched controls, and this difference was significant in women. The excess of coronary heart disease was not explained by an excess of other risk factors such as a high cholesterol, hypertension, smoking, and diabetes. Women with thyroid antibodies had a slightly higher prevalence of coronary heart disease despite the unexpected finding of a lower serum cholesterol. The data point to an association between borderline thyroid function and autoimmunity and coronary heart disease which is not mediated through a raised serum cholesterol.