ABSTRACT
INTRODUCTION: Permanent deep septal stimulation with capture of the left bundle branch (LBB) enables maintenance/restoration of the physiological activation of the left ventricle. However, it is almost always accompanied by the simultaneous engagement of the local septal myocardium, resulting in a fused (nonselective) QRS complex, therefore, confirmation of LBB capture remains difficult. METHODS: We hypothesized that programmed extrastimulus technique can differentiate nonselective LBB capture from myocardial-only capture as the effective refractory period (ERP) of the myocardium is different from the ERP of the LBB. Consecutive patients undergoing pacemaker implantation underwent programmed stimulation delivered from the lead implanted in a deep septal position. Responses to programmed stimulation were categorized on the basis of sudden change in the QRS morphology of the extrastimuli, observed when ERP of LBB or myocardium was encroached upon, as: "myocardial," "selective LBB," or nondiagnostic (unequivocal change of QRS morphology). RESULTS: Programmed deep septal stimulation was performed 269 times in 143 patients; in every patient with the use of a basic drive train of 600 milliseconds and in 126 patients also during intrinsic rhythm. The average septal-myocardial refractory period was shorter than the LBB refractory period: 263.0 ± 34.4 vs 318.0 ± 37.4 milliseconds. Responses diagnostic for LBB capture ("myocardial" or "selective LBB") were observed in 114 (79.7%) of patients. CONCLUSIONS: A novel maneuver for the confirmation of LBB capture during deep septal stimulation was developed and found to enable definitive diagnosis by visualization of both components of the paced QRS complex: selective paced LBB QRS and myocardial-only paced QRS.
Subject(s)
Action Potentials , Arrhythmias, Cardiac/therapy , Bundle of His/physiopathology , Cardiac Pacing, Artificial , Electrophysiologic Techniques, Cardiac , Heart Failure/therapy , Heart Rate , Pacemaker, Artificial , Ventricular Septum/physiopathology , Aged , Aged, 80 and over , Arrhythmias, Cardiac/diagnosis , Arrhythmias, Cardiac/physiopathology , Female , Heart Failure/diagnosis , Heart Failure/physiopathology , Humans , Male , Middle Aged , Predictive Value of Tests , Prospective Studies , Refractory Period, Electrophysiological , Time Factors , Treatment OutcomeABSTRACT
The evidence relating blood pressure to salt intake in humans originates from population studies and randomized clinical trials of interventions on dietary salt intake. Estimates from meta-analyses of trials in normotensive subjects generally are similar to estimates derived from prospective population studies (+1.7-mm Hg increase in systolic blood pressure per 100 mmol increment in 24-hour urinary sodium). This estimate, however, does not translate into an increased risk of incident hypertension in subjects consuming a high-salt diet. The meta-analyses of intervention trials have consistently shown that potassium supplementation is associated with lowering of blood pressure. However, prospective studies relating health outcomes to 24-hour urinary sodium and/or potassium excretion produced inconsistent results. Taken together, available evidence does not support the current recommendations of a generalized and indiscriminate reduction of salt intake at the population level, although the blood-pressure lowering effect of dietary sodium restriction might be of value in hypertensive patients. Potassium supplementation in hypertensive patients or healthy persons is not recommended by the current guidelines, but importance of adhering to healthy diet rich in vegetables and fruits is emphasized.