Clinical Endocrinology (1992) 37,29-33

Cardiac conduction in patients with hypercalcaemia due to primary hyperparathyroidism Milrten Rosenqvlst', Jiirgen Nordenstriimt, Mats AnderssonS and Olof K. EdhagS *Department of Cardiology, Karolinska Institute, Karolinska Hospital; Departments of +Surgery a n d $Internal Medicine, Karolinska Institute, Huddinge University Hospital (Received 18 October 7991; returned for revision 23 January 7992; finally revised 20 February 7992; accepted 9 March 1992)

Summary OBJECTIVE To assess whether hypercalcaemia due to primary hyperparathyroidism is associated wlth signtflcant cardiac arrhythmias. DESIGN AND PARTICIPANTS The prevalence Of cardiac arrhythmias and conduction disturbances was evaluated by 12-lead ECG and 24-hour long-term ECG during presurgical hypercalcaemia and after post-surgical normallzation of serum calcium values in 20 patients wlth prlmary hyperparathyroidism. RESULTS After surgery, meanfSD calcium levels decreased from 2.85 f 0.1 to 2.40 f 0.1 mmol/i (P < 0.001). There was a significant Increase in QT-intervals (0.36f 0.05 vs 0.39 f 0.05) and QTc-intervals(0.38f 0.04 vs 0.42f0.03) after surgery (P< 0.01). Long-term ECG showed no change in the minimal heart rate 4 7 f 8 vs 48 f 7 beatslmin or in the longest RR Interval 1.6f0.5 YS 1.6f0.58 (P NS). There was no difference In the prevalence of supraventricular or ventricular arrhythmias. No episode of high-grade AV-block was observed before surgery. Circadian heart rate rhythm did not change between investigations. CONCLUSIONS It is concluded that moderate hypercalcaemia, In spite of causing a shortening of the repolarlzation phase (QT-interval), has no clinicaily signiflcanteffect on cardiac conduction.

Hypercalcaemia has been shown to diminish cardiac conduction velocity and shorten refractoriness, thereby theoretically facilitating re-entry and the development of complex ventricular arrhythmias. The major electrocardiographic manifestation of elevated calcium levels is the appearance of Correspondence: Dr MIrten Rosenqvist, Department of Cardiology, Thoracic Clinics, Karolinska Institute, Karolinska Hospital, S-104 01 Stockholm, Sweden.

a decrease in the ST-segment, which usually is reflected as a shortening of the QT-interval sometimes associated with a slight prolongation of PR and QRS-intervals (Surawicz, 1966). However, it is not clear from the literature whether moderate hypercalcaemia causes cardiac arrhythmias and whether such rhythm problems can be corrected by a normalization of the calcium level. Surprisingly, clinical observations of conduction disturbances caused by hypercalcaemia are scarce. Although single case reports (Cassagnes et a[., 1979; Voss & Drake, 1967; Crum & Till, 1960; Ginsberg & Schwarz, 1973; Santo et al., 1982; Baumgartl, 1975; Lischer, 1965) describing patients with bradyarrhythmias including atrioventricular nodal conduction defects, sinus node disease and atrial fibrillation have been described, the prevalence of these disturbances is unknown. As hypercalcaemia can induce ventricular arrhythmias in animal experiments (Surawicz, 1966), and single case reports of sudden death among patients with hypercalcaemia have been published (Young & Emerson, 1949; Naik et al., 1963), it has also been postulated that ventricular arrhythmias may be caused by hypercalcaemia. In the present study we have evaluated patients with primary hyperparathyroidism and moderate hypercalcaemia, to investigate whether hypercalcaemia is associated with significant signs of cardiac arrhythmias, and to assess the effect of a normalization of the calcium levels following surgery. Material and methods

Twenty patients (two men and 18 women) with hyperparathyroidism and with a mean SD age of 62 & 9 (range 40-76) years were studied. None of the patients had severe intercurrent disease and none were treated with cardiac chronotropic drugs. Nine patients had a history of treated hypertension and three received thyroxine substitution for hypothyroidism. Two patients had ischaemic heart disease with moderate angina pectoris. One patient had a slight elevation of serum creatinine (189 pmoI/l). No patient had clinical or radiological signs of either cardiac enlargement or congestive heart failure. All patients were in sinus rhythm and none of the patients had signs of left ventricular hypertrophy or ischaemic heart disease on the 12-lead electrocardiogram. None of the patients reported 29

Clinical Endocrinology (1992) 37

30 M. Rosenqvist et al.

Table 1 Blood chemistry before and

Calcium (mmol/l) Ionized calcium (mmol/l) Phosphate (mmol/l) Creatinine (pmol/l) Magnesium (mmol/l) Potassium (mmol/l)

Preop (n= 20)

Postop (n = 20)

2.85f0.14 1.51 f O . 1 1 0.82f0.15 89f31 0.84f 0.08 4.1 f0.4

240f0.13

1.25f0.14 1.02f0.22 87f30 0.82f 0.08 4.1 5 0 . 3 ~

3 months after surgery

P-value

Normal range

Cardiac conduction in patients with hypercalcaemia due to primary hyperparathyroidism.

To assess whether hypercalcaemia due to primary hyperparathyroidism is associated with significant cardiac arrhythmias...
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