A few studies have already demonstrated that LVH results in prolonged and non-uniform ventricular repolarization, increased action potential duration, and delayed ventricular conduction
. [21-23] The prolonged QT interval may be attributed to the increased thickness of the left ventricle wall and to intramural fibrosis, which distorts and prolongs transmural impulse propagation which may be a manifestation of the intraventricular or interventricular conduction delay or block, or it may be due to the downregulation of several potassium currents responsible for repolarization.
However, population-based data in persons with ventricular conduction
defects concluded that the JT adjustment assessed as QTc-QRS "retained a strong residual correlation with ventricular rate making its use ill-advised" .
Sack et al., "Long-term clinical effect of hemodynamically optimized cardiac resynchronization therapy in patients with heart failure and ventricular conduction
delay," Journal of the American College of Cardiology, vol.
Electrocardiogram demonstrated sinus rhythm with normal atrioventricular nodal and ventricular conduction
intervals including PR, QRS, and QTc at baseline.
Some studies have shown that therapy to improve gap junctions can increase ventricular conduction
velocity, delay the onset of spatially discordant alternans, and decrease the susceptibility to arrhythmia [25,26].
This recent interest has mainly been stimulated by the very successful introduction of cardiac resynchronization therapy as a new, device-based treatment option for patients with end-stage heart failure and ventricular conduction
delays in the mid-1990s.
Blocking these channels decreases the slope of phase 0, which also leads to a decrease in the amplitude of the action potential and hence slows the ventricular conduction
Indeed, inappropriate shocks for atrial arrhythmias with rapid ventricular conduction
or for abnormal sensing result in multiple adverse effects including impaired quality of life, psychiatric disturbances, and even provocation of fatal ventricular arrhythmia.
Dodge, "Mechanisms of QRS complex prolongation in man; left ventricular conduction
disturbances," The American Journal of Medicine, vol.
Ventricular hypertrophy is a known risk factor for QT prolongation and altered ventricular conduction
and repolarization (Ben-David et al.
A prolonged QRS interval suggests a diseased ventricular conduction
system and has been associated with increased risk for sudden cardiac death, among other heart disorders.
If the bundle branches are blocked or conduction originates outside of the normal ventricular conduction
fibers, the slower depolarization over alternative pathways results in a wide QRS waveform.