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Significance of QTc Interval in Chronic Hypoparathyroidism and its Correlates
Preeti Namjoshi1, Soma Saha1, Vibhav Sharma2
1Department of Endocrinology and Metabolism, All India Institute of Medical Sciences, New Delhi 110029, India.
Insights
Patients with chronic hypoparathyroidism (cHypoPT) face risks of QTc prolongation and arrhythmias. Maintaining serum total calcium above 8.3 mg/dL is crucial for minimizing these risks.
Area of Science:
- Cardiology
- Endocrinology
- Clinical Biochemistry
Background:
- Chronic hypoparathyroidism (cHypoPT) increases risk of QTc prolongation and arrhythmias due to hypocalcemia.
- Limited data exists on QTc correlates in cHypoPT patients.
Purpose of the Study:
- To investigate the significance of the QTc interval in cHypoPT.
- To identify clinical and biochemical factors associated with QTc prolongation in cHypoPT.
Main Methods:
- Observational cohort study of 88 non-surgical cHypoPT patients.
- Assessment of QTc interval, arrhythmic symptoms, and serum levels of calcium, phosphate, 25(OH)D, and intact parathyroid hormone.
Main Results:
- Mean QTc was 428 ± 34 ms; 13.6% had prolonged QTc.
- Significant inverse correlation between QTc interval and serum total calcium (r = -0.43, P < .001).
- Lower serum calcium and higher prevalence of arrhythmic symptoms in patients with prolonged QTc.
Conclusions:
- A significant proportion of cHypoPT patients experience QTc prolongation and arrhythmic symptoms.
- Close monitoring for arrhythmias and QTc prolongation is essential in cHypoPT.
- Maintaining serum total calcium ≥ 8.3 mg/dL may reduce arrhythmia risk.
Context:
Hypocalcemia predisposes patients with chronic hypoparathyroidism (cHypoPT) to an increased risk of QTc prolongation and life-threatening arrhythmias. Information on clinical and biochemical correlates of QTc in cHypoPT is limited.
Objective:
To assess the significance of QTc interval in chronic hypoparathyroidism and its correlates.
Methods:
This was an observational cohort study at a tertiary care center. Eighty-eight nonsurgical patients with cHypoPT (mean age 44.1 ± 15.4 years, 45 males) were assessed for QTc interval and its possible correlates including arrhythmic symptoms (palpitation/giddiness/syncope), serum total calcium, phosphate, 25(OH)D, and intact parathyroid hormone.
Results:
The mean QTc in the HypoPT cohort was 428 ± 34 ms with 13.6% having prolonged QTc. There was a significant inverse correlation between QTc interval and serum total calcium measured on the same day (r = -0.43, P < .001). The mean serum total calcium was significantly lower in patients with prolonged QTc (7.05 ± 1.94 vs 8.49 ± 1.01 mg/dL, P = .02). Of patients with cHypoPT 21.6% had arrhythmic symptoms. They had significantly higher mean QTc (P = .02) and also tended to have lower mean serum total calcium during follow-up (P = .06). In multivariable regression, female gender, higher current age, higher body mass index, and low serum total calcium showed significant association with prolonged QTc. For every mg/dL decrease in serum total calcium, QTc increased by 13 ms. Receiver operating characteristic analysis revealed serum total calcium at cut-off of 8.3 mg/dL discriminated prolonged QTc with area under the curve being 0.72 (95% CI 0.51, 0.93).
Conclusion:
One-fifth of patients with cHypoPT had arrhythmic symptoms and a significant proportion had prolonged QTc. This highlights the need for close monitoring of patients with cHypoPT for arrhythmic symptoms and QTc prolongation. The serum total calcium should be maintained to at least 8.3 mg/dL to minimize the risk of potentially life-threatening arrhythmia in cHypoPT.
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