Converting enzyme inhibition normalizes QT interval in spontaneously hypertensive rats

Area of Science:

• Cardiology
• Physiology
• Pharmacology

Background:

• The QT interval, a measure of cardiac repolarization, is not well-characterized in rats.
• Spontaneously hypertensive rats (SHR) develop pressure-overloaded hearts.
• Assessing QT interval changes in response to cardiac mechanical overload is crucial.

Purpose of the Study:

• To quantify the QT interval in spontaneously hypertensive rats (SHR).
• To investigate the effect of converting enzyme inhibition on QT interval and cardiac remodeling in SHR.
• To establish SHR as a model for studying QT interval adaptations during mechanical overload.

Main Methods:

• Implanted telemetry system for ECG and RR interval recording in freely moving rats.
• Manual QT duration determination using a calibrated gauge.
• Echocardiography for sequential assessment of left ventricular mass.
• Time-frequency domain analysis for heart rate variability evaluation.

Main Results:

• 12-month-old SHR exhibited higher left ventricular mass, QT, and RR intervals compared to Wistar rats.
• Trandolapril treatment (2 months) reduced systolic blood pressure, left ventricular mass, and QT interval in SHR.
• A positive correlation was observed between QT interval and left ventricular mass.
• Heart rate variability remained unchanged throughout the study.

Conclusions:

• The QT interval in SHR reflects phenotypic changes associated with mechanical heart overload.
• SHR are suitable for longitudinal QT interval studies, aiding in vivo determination of cardiac adaptation.
• Converting enzyme inhibition demonstrates a reversible increase in QT interval in pressure-overloaded hearts.