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| Year : 1983 | Volume
: 29
| Issue : 3 | Page : 160-1 |
Effect of propranolol on the electrocardiogram in hypothyroidism.
Shah SJ, Fonseca VV, Rais NN, Sayeed AA, Bhandarkar SD
How to cite this article:
Shah S J, Fonseca V V, Rais N N, Sayeed A A, Bhandarkar S D. Effect of propranolol on the electrocardiogram in hypothyroidism. J Postgrad Med 1983;29:160 |
How to cite this URL:
Shah S J, Fonseca V V, Rais N N, Sayeed A A, Bhandarkar S D. Effect of propranolol on the electrocardiogram in hypothyroidism. J Postgrad Med [serial online] 1983 [cited 2023 Mar 31];29:160. Available from: https://www.jpgmonline.com/text.asp?1983/29/3/160/5526 |
In this country, T3, T4 and TSH radioimmunoassays are not yet available at many places. Physicians still use normalization of ECG with thyroxine as one of the diagnostic criteria of hypothyroidism. In some elderly hypothyroid patients, who may have concomitant ischemic or hypertensive heart disease, it may be advisable to start propranolol either along with or before thyroxine, in order to prevent possible worsening of the cardiac status by thyroxine.[1], [2] This study was undertaken to find out whether propranolol would change the ECG pattern of hypothyroidism and thus interfere with assessment of ECG response to thyroxine.
Twelve patients with clinically frank hypothyroidism were studied. All patients were females and their ages ranged from 25 to 51 years. None of them had hypertension or angina pectoris. All had low T3 charcoal uptake. The ECG showed sinus bradycardia, low voltage of QRS complexes and generalised flattening of T waves in all the patients.
The first 5 patients were prescribed propranolol, 10 mg three times a day for one week, 20 mg three times a day for one week, 30 mg three times a day for one week and 40 mg three times a day for one week. They reported to the clinic at weekly intervals for detailed clinical evaluation and repeat ECG. During the course of propranolol treatment, three patients developed mild dyspnoea but were able to complete the prescribed course of propranolol. Two patients became severely breathless, one on 10 mg three times a day and the other on 20 mg three times a day. In none of the above 5 patients, the repeat ECG showed any significant change compared to the baseline ECG. In 3 patients who completed 4 weeks of propranolol, the drug was continued in the dose of 40 mg three times a day and 1-thyroxine sodium was added in the dose of 0.1 mg once a day for a week, followed by 0.2 mg once a day. In 2 patients who became severely breathless, propranolol was omitted and 1-thyroxine sodium was prescribed as above. After starting treatment with 1-thyroxine, all the five patients improved clinically and the ECG reverted to normal in 4 to 8 weeks.
The remaining 7 patients received 10 mg of propranolol three times a day for one week. None of them developed breathlessness. At the end of this period, the ECG showed no change in QRS complexes and in T waves compared to the pretreatment ECG in any of them. They were then advised to continue propranolol in the same dose and 1-thyroxine sodium was added in the dose of 0.3 mg once a day. They continued to report to the clinic weekly for clinical evaluation and repeat ECG. The ECG became normal in 2 to 3 weeks.
None of the 12 patients developed angina during thyroxine administration.
Some hypothyroid patients develop angina pectoris for the first time when replacement therapy with thyroxine is started. The prophylactic use of propranolol has, therefore, been recommended in elderly patients with hypothyroidism.[1], [2] When T4 and TSH assays are not available and the physician has to depend upon the normalization of ECG on thyroxine treatment for diagnosis of hypothyroidism, it is important to establish that propranolol itself does not alter the abnormal ECG of hypothyroidism. The present study suggests that administration of propranolol does not bring about any changes in the ECG of hypothyroid patients. Further, it may increase the safety of thyroxine treatment in these patients.
We thank Dr. C. K. Deshpande, the Dean, Seth G.S. Medical College and K.E.M. Hospital for allowing us to publish this data.
| 1. | Capiferri, R. and Evered, D.: Investigation and treatment of hypothyroidism. Clin. Endocrinol. & Metab., 8: 43-44, 1979.  |
| 2. | Editorial: Management of angina and hypothyroidism. Brit. Med. I., 282: 1818-1819, 1981. |
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