Stimulation of the left ventricle through the coronary sinus with a newly developed 'over the wire' lead system--early experiences with lead handling and positioning.

AIMS: This report describes the initial clinical results with a newly designed guiding catheter and an 'over the wire' pacing lead based on angiolasty technology to stimulate the left ventricle using the transvenous route via the coronary sinus (OTW-CV lead). METHODS AND RESULTS: In 75% of the 15 patients (6 males, 9 females, mean age of 53 +/- 9 years) with congestive heart failure, access to coronary sinus required less than 2 min; in one patient. the attempt failed. Mean R wave amplitudes plus or minus the standard deviation, measured at apical, mid-ventricular and basal positions the anterior (11.4 +/- 9.2, 10.8 +/- 6.2, 9.3 +/- 6.3 mV) and lateral or posterior veins (10.1 +/- 10.7, 8.6 +/- 6.4, 7.7 +/- 4.3 mV) showed a trend favouring the apex without statistical significance. Pacing impedance, measured at the same sites and vein tributaries, ranged from 670 +/- 191 to 915 +/- 145 ohms. Pacing thresholds measured at apical and mid ventricular sites were significantly lower than at the base in the anterior vein 2.5 +/- 2.8 and 2.8 +/- 1.8 vs 5.6 +/- 2.7 V at 0.5 ms, P<0.001). Thresholds in the lateral/posterior veins showed a similar trend but did not reach statistical significance (3.0 +/- 1.7, 3.6 +/- 1.4 +/- 1.8 V at 0.5 ms). In patients, in whom thresholds were determined in more than one vein, the 'best' mean threshold was 1.6 +/- 0.7 V. CONCLUSION: The new 'over the wire' lead and guiding catheter system allows uncomplicated access to the coronary sinus and the depth of the coronary vein tributaries. Left ventricular sensing and pacing thresholds are acceptable for chronic use in implanted cardiac rhythm management systems.

Effect of pacing chamber and atrioventricular delay on acute systolic function of paced patients with congestive heart failure. The Pacing Therapies for Congestive Heart Failure Study Group. The Guidant Congestive Heart Failure Research Group.

BACKGROUND: Previous studies of pacing therapy for dilated congestive heart failure (CHF) have not established the relative importance of pacing site, AV delay, and patient heterogeneity on outcome. These variables were compared by a novel technique that evaluated immediate changes in hemodynamic function during brief periods of atrial-synchronous ventricular pacing. METHODS AND RESULTS: Twenty-seven CHF patients with severe left ventricular (LV) systolic dysfunction and LV conduction disorder were implanted with endocardial pacing leads in the right atrium and right ventricle (RV) and an epicardial lead on the LV and instrumented with micromanometer catheters in the LV, aorta, and RV. Patients in normal sinus rhythm were stimulated in the RV, LV, or both ventricles simultaneously (BV) at preselected AV delays in a repeating 5-paced/15-nonpaced beat sequence. Maximum LV pressure derivative (LV+dP/dt) and aortic pulse pressure (PP) changed immediately at pacing onset, increasing at a patient-specific optimal AV delay in 20 patients with wide surface QRS (180+/-22 ms) and decreasing at short AV delays in 5 patients with narrower QRS (128+/-12 ms) (P<0.0001). Overall, BV and LV pacing increased LV+dP/dt and PP more than RV pacing (P<0.01), whereas LV pacing increased LV+dP/dt more than BV pacing (P<0.01). CONCLUSIONS: In this population, CHF patients with sufficiently wide surface QRS benefit from atrial-synchronous ventricular pacing, LV stimulation is required for maximum acute benefit, and the maximum benefit at any site occurs with a patient-specific AV delay.

Transvenous biventricular pacing for heart failure: can the obstacles be overcome?

Despite increasing evidence of hemodynamic benefit and long-term improvement in clinical status of congestive heart failure (CHF) patients with left ventricular and biventricular pacing, the risks and technical limitations of placing a permanent left ventricular pacing lead have prevented widespread clinical adoption of this therapy. Results of this and other recent investigations suggest it is necessary to target specific sites on the left ventricle to maximize hemodynamic benefit. However, limitations and variations of coronary vein anatomy, as well as patient safety, lead dislodgement, pacing thresholds, lead handling, and ease-of-use issues, present technical challenges for current transvenous permanent pacing lead designs. However, a new transvenous lead system based on an over-the-wire design appears to solve many of these problems and has proved feasible in acute clinical studies.

Effects of acute changes in canine LV-chamber volume and shape on accuracy of impedance catheter estimates of LV-chamber volume.

The accuracy with which a multiple-electrode impedance catheter (IC) tracks instantaneous global, in-situ left ventricular (LV) volumes was tested in 13 anesthetized dogs scanned in the Dynamic Spatial Reconstructor (DSR), a fast volumetric computed tomographic (CT) scanner. All dogs were scanned during control conditions and during an acute hemodynamic intervention. Hypertonic saline calibrations were performed for the IC prior to each DSR scan. In six of the dogs the IC-derived LV end-diastolic volume (Y) correlated with the DSR-derived global LV end-diastolic volume (X) as follows: end-diastolic volume, Y = 1.01X - 9.9, r = 0.812. The IC-derived LV end-diastolic volume, under control conditions, correlated with the DSR-derived truncated (i.e., that region of the LV chamber between the proximal and distal electrodes of the IC catheter) LV end-diastolic volume, Y = 1.00X + 17.4, r = 0.803. Under reduced preload the relation was Y = 1.3X - 15.26, r = 0.911. The segmental volume (between adjacent sensing electrodes on the IC) at the basal portion of the LV correlated poorly (Y = 1.88X + 3.3, r = 0.459 etc.), but correlated better at mid- and more apical LV levels (Y = 0.97X + 2.7, r = 0.762). Correlations between segmental stroke volumes were similar at basal (Y = 1.31X + 1.60, r = 0.815) and mid- and more apical levels (Y = 1.42X + 0.11, r = 0.763). Stroke volume during acute ischemia (two dogs) was Y = 1.33X - 1.41, r = 0.717; during acutely decreased preload (four dogs) it was Y = 1.24X - 2.88, r = 0.572). Thus, the IC tracks the changes in LV-chamber volume throughout a cardiac cycle quite well under a variety of conditions, but accuracy deteriorates as the shape of the LV chamber changes in response to changes in hemodynamic loading or local myocardial ischemia.

Physiologic benefits of rate responsiveness.

Increases in metabolic demand in response to routine activities and exercise are met through greater cardiac output and oxygen delivery. Patients with fixed-rate pacemakers cannot increase heart rate and must rely solely on increases in stroke volume to provide the necessary adjustments in cardiac output. These compensatory stroke volume increases limit the fixed-rate pacemaker patient's ability to meet the demand of their daily routine. A physiological, rate responsive pacemaker was studied and it was found to increase maximum exercise tolerance from 4.4 +/- .62 METS paced VVI at 65 ppm to 8.1 +/- .71 METS when the same patients were paced rate responsively at an average rate of 91 +/- 3.8 ppm. Animal studies were used to quantify the limitation in stroke volume reserve. Maximum increases of 55.8 +/- 3.7% over resting values were seen in animals in complete heart block at pacing rates of 100 ppm during strenuous exercise. Higher pacing rates increased cardiac output at the same exercise intensity, from 4.94 +/- .72 lpm at 100 ppm to 7.66 +/- 1.02 lpm at 250 ppm. A pacemaker that increases pacing rate in response to greater metabolic demand will maintain stroke volume and end-diastolic volume at near normal values while providing significant improvement in cardiac output and work capacity.