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Long-term thiazide treatment for mild hypertension increases ventricular ectopic beats (VEBs), especially complex types. This arrhythmia risk is linked to lower serum potassium levels.
Area of Science:
- Cardiology
- Clinical Pharmacology
- Hypertension Management
Background:
- Ambulatory electrocardiogram (ECG) monitoring is crucial for assessing cardiac arrhythmias.
- Thiazide diuretics are commonly prescribed for mild hypertension.
- The long-term effects of thiazides on ventricular arrhythmias require further investigation.
Purpose of the Study:
- To evaluate the prevalence of ventricular ectopic beats (VEBs) during long-term thiazide therapy in patients with mild hypertension.
- To compare the incidence of VEBs in thiazide recipients versus placebo.
- To explore the relationship between VEBs and serum potassium levels.
Main Methods:
- Direct visual interpretation of 24-hour ambulatory ECG recordings.
- Prospective study involving participants from the Medical Research Council mild hypertension trial.
- Analysis of both unselected and selected hypokalaemic participants.
Main Results:
- Long-term thiazide treatment (24 months) was associated with a higher prevalence of VEBs (≥5/hour) compared to placebo (32% vs. 20% daytime, 23% vs. 9% night-time).
- Special VEBs (multifocal, couplets, R-on-T, bigeminy) were more frequent with long-term thiazide use (33%) than placebo (15%).
- VEBs were common in hypokalaemic participants on thiazides (45%) and negatively correlated with serum potassium.
Conclusions:
- Long-term thiazide therapy for mild hypertension may increase the risk of ventricular ectopic beats.
- Hypokalaemia induced by thiazides could contribute to the increased prevalence of VEBs.
- Close monitoring of cardiac rhythm and serum potassium is recommended for patients on long-term thiazide treatment.
Abstract:
Direct visual interpretation of a daytime and night-time hour of ambulatory ECG recording was possible in 287 of 324 Medical Research Council mild hypertension trial participants. The prevalence of arrhythmias in 103 unselected participants was similar before and 8 weeks after initiation of placebo or thiazide treatment. However, in 164 unselected participants studied during long term therapy (average, 24 months) the prevalence of daytime and night-time ventricular ectopic beats (VEBs) greater than or equal to 5/hour was greater in thiazide recipients (32% and 23%, respectively) than in their placebo counterparts (20% and 9%, respectively). In addition, special VEBs such as multifocal beats, couplets. R-on-T beats and bigeminy were more common during long term thiazide (33%) than placebo (15%) treatment. Ventricular ectopic beats greater than or equal to 5/hour and special VEBs were also common (45% and 40%, respectively) in 20 selected hypokalaemic participants studied during long term thiazide therapy. In pooled data, daytime and night-time VEBs were negatively correlated with serum potassium (p = 0.04 and p = 0.03, respectively) but the correlation coefficients were small (r = -0.11 and r = -0.12, respectively).