Cardiac repolarization and its relation to ventricular geometry and rate in reverse remodelling during antihypertensive therapy with irbesartan or atenolol: results from the SILVHIA study

Effects of Calcium, Magnesium, and Potassium Concentrations on Ventricular Repolarization in Unselected Individuals

BACKGROUND

Subclinical changes on the electrocardiogram are risk factors for cardiovascular mortality. Recognition and knowledge of electrolyte associations in cardiac electrophysiology are based on only in vitro models and observations in patients with severe medical conditions.

OBJECTIVES

This study sought to investigate associations between serum electrolyte concentrations and changes in cardiac electrophysiology in the general population.

METHODS

Summary results collected from 153,014 individuals (54.4% women; mean age 55.1 ± 12.1 years) from 33 studies (of 5 ancestries) were meta-analyzed. Linear regression analyses examining associations between electrolyte concentrations (mmol/l of calcium, potassium, sodium, and magnesium), and electrocardiographic intervals (RR, QT, QRS, JT, and PR intervals) were performed. The study adjusted for potential confounders and also stratified by ancestry, sex, and use of antihypertensive drugs.

RESULTS

Lower calcium was associated with longer QT intervals (-11.5 ms; 99.75% confidence interval [CI]: -13.7 to -9.3) and JT duration, with sex-specific effects. In contrast, higher magnesium was associated with longer QT intervals (7.2 ms; 99.75% CI: 1.3 to 13.1) and JT. Lower potassium was associated with longer QT intervals (-2.8 ms; 99.75% CI: -3.5 to -2.0), JT, QRS, and PR durations, but all potassium associations were driven by use of antihypertensive drugs. No physiologically relevant associations were observed for sodium or RR intervals.

CONCLUSIONS

The study identified physiologically relevant associations between electrolytes and electrocardiographic intervals in a large-scale analysis combining cohorts from different settings. The results provide insights for further cardiac electrophysiology research and could potentially influence clinical practice, especially the association between calcium and QT duration, by which calcium levels at the bottom 2% of the population distribution led to clinically relevant QT prolongation by >5 ms.

Subclinical ventricular repolarization abnormality in uncontrolled compared with controlled treated hypertension

Background

Antihypertensive medications have variable effects on the duration of the QT interval. This study aims to demonstrate the subclinical ventricular conduction defect in treating hypertensive patients taking in consideration the status of the blood pressure control with the antihypertensive agents.

Methods

This cross-section study was performed at the Departments of Physiology and Pharmacology, College of Medicine, Al-Mustansiriya University, Baghdad, Iraq. A total number of 97 hypertensive patients (30 males and 67 females) were eligible to enroll in the study. The patients were grouped into controlled hypertension (Group I) and uncontrolled hypertension (Group II). Each participant is subjected to the electrocardiograph (ECG) investigation. A QT nomogram plot used to identify the patients who are vulnerable or at risk of developing cardiac arrhythmias.

Results

There were no significant differences in the values of the electrocardiogram determinants between Group I and Group II. Abnormal prolonged QTcB interval observed in 18 out of 80 (22.5%) patients of Group II compared with 4 out of 17. The JT index value of ≥112 was observed in 20 out of 80 (25%) patients of Group II compared with 6 out of 17 (35.3%) patients of Group I. A significant correlation between the QTcB duration with JT index observed in both Groups I and II.

Conclusion

Patients with hypertension have variability in ventricular repolarization (QTcB and JT) irrespective of their blood pressure control putting them at higher risk of cardiac arrhythmias.

Markers of inflammation, endothelial activation, and arterial stiffness in hypertensive heart disease and the effects of treatment: results from the SILVHIA study

We assessed the contribution of blood pressure (BP), inflammation, and endothelial activation to the development of structural vascular and cardiac changes in hypertension. Furthermore, the effects of antihypertensive therapy were studied. We studied 114 patients with hypertension and left ventricular hypertrophy and 38 matched hypertensive subjects without cardiac hypertrophy and 38 normotensive subjects. The group with hypertension and cardiac hypertrophy were randomized to treatment with an angiotensin receptor blocker (irbesartan) or a beta-adrenergic receptor blocker (atenolol) for 48 weeks. Markers of inflammation (high-sensitive C-reactive protein, interleukin-6, leukocyte counts), vascular function (ambulatory aortic stiffness index, arterial compliance, and pulse pressure), and endothelial activation (E-selectin, intracellular adhesion molecule-1, vascular adhesion molecule-1) were assessed. Markers of inflammation and arterial stiffness were lowest in the normotensive group and highest in patients with hypertensive heart disease; endothelial markers were similar between groups. Inflammation was independently related to BP. Markers of arterial stiffness were independently related to BP and to a lesser extent to left ventricular mass. Antihypertensive treatment improved arterial compliance; inflammatory and endothelial markers remained unchanged. In conclusion, markers of inflammation and arterial stiffness are independently related to BP. Antihypertensive therapy seems to improve arterial stiffness, but effects on markers of inflammation and endothelial activation are small.

Discrepant regulation of QT (QTc) interval duration by calcium channel blockade and angiotensin converting enzyme inhibition in experimental hypertension

Antihypertensive treatment may reduce prolonged QT duration in hypertension. Generally, the reductions of blood pressure and/or of cardiac mass are believed to be the responsible factors. However, drugs are not equivalent in QT modulation despite similar antihypertensive and antihypertrophic action. We investigated the effect of a calcium channel blocker, lacidipine and an angiotensin-converting enzyme inhibitor, enalapril on QT duration in rats. Normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were treated with lacidipine (at the dose of 1.5 mg/kg per day for WKY and 3 mg/kg per day for SHR) or enalapril (5 mg/kg per day for WKY and 10 mg/kg per day for SHR) during 8 weeks. Tail-cuff systolic blood pressure (sBP), left ventricular weight (LVW), vascular function of isolated aorta and mesenteric artery and duration of QT (and QTc) interval on Frank electrocardiograms were evaluated. As expected, untreated SHR showed elevated sBP, impaired vascular reactivity, increased LVW and prolonged QT when compared with WKY (p < 0.05). After treatment, both agents markedly improved vascular reactivity and reduced sBP in SHR (p < 0.05). Additionally, enalapril reduced LVW in both hypertensive (by 17%; p < 0.05) and normotensive rats (by 13%; p < 0.05) and, consequently, corrected QT duration in SHR. Interestingly, lacidipine also reduced LVW in SHR (by 9%; p < 0.05), but without influence on prolonged QT. Moreover, lacidipine had no effect on LVW in WKYs but prolonged their QT interval (by 10%; p < 0.05). In conclusion, lacidipine did not reverse a progressive prolongation of QT in SHR, despite sBP lowering and LVW reduction. Thus, the lowering of blood pressure and/or reduction of LVW are not sufficient per se to normalize ventricular repolarization in hypertensive cardiac disease. More likely, modulation of QT prolongation by antihypertensive drugs is a function of their complex action on blood pressure, vascular function, cardiac mass and on reflex neurohumoral activation.

Understanding heart failure with preserved ejection fraction: clinical importance and future outlook

Heart failure (HF) with preserved ejection fraction (HF-PEF) accounts for approximately one half of all HF patients admitted with acute decompensated HF and carries a significant morbidity and mortality burden. This condition, however, has been largely understudied because it is difficult to diagnose, and management guidelines are still being discussed. This article provides an overview of HF-PEF and its pathophysiology, diagnosis, and treatment, with a focus on clinical trials using renin-angiotensin-aldosterone system (RAAS) blockers. Inhibitors of the RAAS have been studied in HF-PEF to determine whether their benefits extend beyond blood pressure control. However, the 3 trials conducted to date (CHARM-Preserved, PEP-CHF, and I-PRESERVE) with candesartan, perindopril, and irbesartan, have failed to demonstrate significant morbidity and mortality benefits. Although no agent has proven statistically significant benefits in morbidity and mortality in HF-PEF, recent studies have added to the breadth of clinical data and understanding of the demographics of these patients.