June 26, 2011

Congestive heart failure in subjects with thyrotoxicosis in a black community

Authors: R C Anakwue, B J C Onwubere, B C Anisiuba, V O Ikeh, A Mbah, S O Ike; Department of Medicine, College of Medicine, University of Nigeria Enugu Campus

Introduction: Thyroid hormone has profound effects on a number of metabolic processes in virtually all tissues but the cardiovascular manifestations are prominent usually creating a hyperdynamic circulatory state. Thyrotoxicosis is not a common cause of congestive heart failure among black communities.

Objectives: To determine the hospital prevalence, clinical characteristics and echocardiographic findings in patients with thyrotoxicosis who present with congestive heart failure (CCF) in the eastern part of Nigeria.

Subjects and methods: A total of 50 subjects aged 15 years and above who were diagnosed as thyrotoxic following clinical and thyroid function tests were consecutively recruited. Fifty age- and sex-matched controls with no clinical or biochemical evidence of thyrotoxicosis and no comorbidities were used as controls. Two-dimensional echocardiography was carried out on all the subjects. CCF was determined clinically and echocardiographically.

Definitions: The diagnosis of thyrotoxicosis was established in the presence of a serum free T3 >4.2 pg/L and a concomitant suppressed TSH of <0.5 μU/mL. Left ventricular systolic dysfunction was defined by any of the following: (i) left ventricular ejection fraction (LVEF) <50%, (ii) fractional shortening (FS) <18%, (iii) cardiac index <2.8 L/min/m2, (iv) cardiac output <4 L/min, (v) mean velocity of circumferential fiber shortening <1.02 circ/sec, and (vi) peak aortic systolic velocity <72 cm/sec. Dilated thyrotoxic heart muscle disease was defined as (i) end diastolic diameter >6.0 cm, (ii) end systolic diameter >2.5 cm, (iii) LVEF <50%, and (iv) FS <18%.

Results: Eight patients (5 females and 3 males) out of a total of 50 thyrotoxic patients presented with congestive heart failure.

Echocardiographic findings: Echocardiography showed that 5 patients had ejection fraction (LVEF) of <50%. Fractional shortening (FS) of <18% was found in 6 patients (12%), cardiac index of <2.8 L/min/m2 in 5 patients, cardiac output of <5 L in 5 patients (10%), velocity of circumferential fiber shortening of <1.02 circ/sec in 5 patients (10%), aortic maximum velocity of <72 cm/sec in 5 patients (10%). Three of the thyrotoxicosis patients in heart failure clinically, had normal LVEF and FS (50%–75%). Thyrotoxicosis patients without heart failure who had normal systolic function (31 patients – 62%) and enhanced systolic function (11 patients – 22%). Thyrotoxicosis patients in heart failure had significantly lower systolic function than control.
Echocardiography showed that the 5 patients who had LVEF of <50% also had dilatation of other chambers of the heart. A two-dimensional echogram showing dilated heart chambers in thyrotoxicosis is shown in Figure 2. No echocardiographic findings indicating abnormal systolic dysfunction were found in the control group.
Electrocardiography showed that two out of the five patients with LVEF of ,50% were in atrial fibrillation.

Conclusion: The study revealed that congestive heart failure can occur in thyrotoxicosis in spite of the associated hyperdynamic condition. The underlying mechanism may include direct damage by autoimmune myocarditis, congestive circulation secondary to excess sodium, and fluid retention.

Keywords: thyrotoxicosis, congestive heart failure, echocardiography, black community
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