Effect of left ventricular function on long-term left ventricular pacing and sensing threshold.

BACKGROUND: The effect of left ventricular (LV) systolic function on the long-term left ventricular pacing and sensing threshold is unclear. METHODS AND RESULTS: We studied the effect of LV ejection fraction (LVEF) on the LV pacing and sensing threshold in 56 patients (mean age: 70.2 +/- 10.5 years) underwent permanent LV pacing using a self-retaining coronary sinus lead (Model 1055 K, St Jude Medical, USA). In 49 patients, the LV lead was implanted for conventional pacemaker indication (sick sinus syndrome = 14, heart block = 26 or slow atrial fibrillation = 9). The remaining 7 patients were implanted for congestive heart failure. The LV pacing and sensing threshold, and lead impedance were compared between patients with LVEF <40% (Group 1, n = 28) and LVEF >40% (Group 2, n = 28) during implant and at 3-month follow up. The LV pacing lead was successfully implanted in all patients without any lead dislodgement on follow-up. At implant, Group 1 patients had a significant lower R wave amplitude, but similar LV pacing threshold and lead impedance as compared to Group 2. However, at 3-month follow-up, Group 1 patients had a significantly higher LV pacing threshold compared to Group 2 patients. There were no significant differences in the sensing threshold and lead impedance between the two groups. Furthermore, there was also a significant interval increase in LV pacing threshold in Group 1 patients (0.94 +/- 0.12 V) after 3 months, but not in Group 2 patients (0.16 +/- 0.08 V, p < 0.01). CONCLUSIONS: The results of this study suggest that the LV systolic function has a significant impact on the long-term LV pacing threshold. The long-term left ventricular pacing threshold in patients with left ventricular systolic dysfunction increased after implant and was higher than patients with normal left ventricular systolic function.

Do clinical and angiographic parameters predict failure of medical therapy in patients suitable for coronary angioplasty?

AIMS: Recent studies have suggested that patients with coronary disease suitable for angioplasty have an equally good outcome with medical therapy if clinically stable. Complex lesion morphology may predict acute events without intervention and stenosis severity influences the degree of collateralisation. This study was designed to assess the influence of these factors on clinical outcome. METHODS AND RESULTS: A retrospective review of patients suitable for angioplasty who were randomised to initial medical therapy as part of a multicentre study. Angiograms were reviewed for lesion characteristics, TIMI flow grade, and degree of collateralisation. Angiograms were available on 79 patients (13 female, 66 male). Mean age was 54.8 years (range 43-68) in the group crossing-over to revascularisation, and 58.4 (range 37-78) in the group who did not (P=ns). Seventeen patients crossed-over (two to CABG, 15 to PTCA) at 5.4 months (range 0-10) after initial angiography. Disease progression had occurred in 10/17 patients (58.8%), three of whom developed a new occlusion. Collateralisation was more likely in smokers, independent of lesion severity (P<0.05). Time to cross-over was not influenced by progression of disease. Crossing-over was not affected by age, diabetic status, cholesterol level, vessel involved, lesion severity, TIMI flow, lesion morphology, collateralisation, or the number of vessels diseased, but was more likely in females (P<0.05). CONCLUSION: This group of patients generally does well with medical therapy. Whilst the numbers are relatively small, there does not appear to be any reliable prospective marker, including the presence of spontaneous collateral channels on diagnostic angiography, to indicate which patients will fail medical therapy and require revascularisation.

Heart rate dependency of pulse pressure amplification and arterial stiffness.

BACKGROUND: Pulse pressure and aortic pulse wave velocity, measures of arterial stiffness, are both important determinants of cardiovascular risk. However, assessment of peripheral pulse pressure does not always provide a reliable measure of changes in central pulse pressure or arterial stiffness. The aim of the present study was to assess the effect of acute changes in heart rate on arterial stiffness and on peripheral and central pulse pressure in healthy subjects. METHODS: Twenty subjects (age range, 20 to 72 years) were studied at cardiac catheterization. Pulse wave analysis was used to determine central pressure, augmentation index (AIx), a measure of systemic arterial stiffness, and aortic pulse wave velocity (PWV) during right atrial pacing (80 to 120 beats/min). RESULTS: Pulse pressure amplification increased during pacing due to a reduction in central pressure augmentation. AIx was significantly and inversely related to heart rate (r = -0.70, P < .001) due to an alteration in the relative timing of the reflected pressure wave, rather than a reduction in arterial stiffness, as PWV did not change. CONCLUSIONS: These data suggest that peripheral pulse pressure does not provide an accurate assessment of changes in central hemodynamics in relation to changes in heart rate, and that aortic stiffness is not affected by acute changes in heart rate.