Arrhythmic burden of long-term postsurgical hypoparathyroidism assessed with 24-hour Holter ECG

Postsurgical hypoparathyroidism is associated with an increased cardiovascular risk, however an increased arrhythmic risk in this population is controversial.

Twenty-two postmenopausal women with postsurgical hypoparathyroidism and 22 healthy postmenopausal women of the same age were enrolled. Each subject underwent blood tests, standard 12-lead ECG, 24-hour Holter ECG and echocardiographic measurements. The exclusion criteria were: previous cardiovascular disease, arrhythmias, diabetes mellitus, kidney failure, use of drugs that may interfere with cardiac conduction.

Time since diagnosis of postsurgical hypoparathyroidism was 19.33 ± 8.82 years. As expected, serum calcium and PTH levels were significantly lower in hypoparathyroid patients compared to controls, while phosphorus was higher (all p < 0.05). ECG parameters were within normal values in both groups. A higher number of hypoparathyroid patients had significantly more supraventricular and ventricular premature beats compared to controls (p < 0.05). An index of heart variability, predominantly of parasympathetic activity, such as the root mean square of the difference between successive RR intervals was significantly lower in hypoparathyroid patients compared to controls (21.09 ± 9.84 vs 33.0 ± 17.89 msec, p = 0.009). All the echocardiographic parameters were within the normal limits. The only statistically significant difference between groups was a lower ejection fraction (EF) in the hypoparathyroid group compared to controls (57.5% ± 2.98 vs 64.85% ± 6.09, p < 0.0001). A longer time since diagnosis of hypoparathyroidism was only positively associated with heart rate: B = 0.45, QRS: B = 0.66 and negatively with EF:B = -0.64 (all p < 0.05).

24-hour ECG Holter demonstrated an increase in arrhythmia in postmenopausal women with long-term postsurgical hypoparathyroidism in the absence of long QT or cardiac structural abnormalities.