A opção de programação rate drop response (resposta à queda de freqüência) previne a hipotensão ortostática em pacientes idosos, portadores de marcapasso e com incompetência cronotrópica? / Transient overdrive pacing upon standing prevents orthostatic hypotension in elderly pacemaker patients with chronotropic incompetence

Introdução: pacientes idosos, portadores de marcapasso e com incompetência cronotrópica (IC) podem apresentar hipotensão em posição ortostática (HO). Objetivo: determinar se o aumento transitório da freqüência cardíaca, por meio da opção de programação rate drop response (resposta à queda da freqüência cardíaca), previne...

Transient overdrive pacing upon standing prevents orthostatic hypotension in elderly pacemaker patients with chronotropic incompetence.

BACKGROUND: Elderly pacemaker patients with chronotropic incompetence (CI) may experience orthostatic hypotension (OH) upon standing. The objective of this study was to determine whether a transient increase in heart rate (HR) by overdrive pacing upon standing prevents OH in elderly pacemaker patients. METHODS: We studied the effect of transient overdrive pacing upon standing in mitigating the drop in blood pressure (BP) in 62 pacemaker patients (77 +/- 6 years, 32 F) implanted with DDD pacemaker for sick sinus syndrome (n = 40) or atrioventricular block (n = 22). All patients underwent two standing procedures in random order: a control, with backup (60 bpm) pacing and another with overdrive DDD pacing (at 35 bpm above their baseline rate) for 2 minutes upon standing. Systolic (SBP) and diastolic blood pressure (DBP) and HR were measured while supine (baseline) and 1, 2, and 3 minutes after standing. OH was defined as a drop in SBP > or = 20 mmHg or DBP > or = 10 mmHg during standing. Chronotropic incompetence (CI) was defined as an absence of HR increase of > or = 10 bpm during standing. RESULTS: A total of 17 (27%) patients developed OH upon standing during backup pacing. Baseline clinical characteristics (age, sex, prevalence of diabetes, use of vasoactive medications, and sick sinus syndrome) were similar between patients with or without OH. In patients with or without OH, transient overdrive pacing upon standing increased HR and DBP as compared with baseline (P < 0.05). However, in patients with OH, transient overdrive pacing did not prevent decrease in SBP upon standing and avoided the development of OH in only 10/17 patients (59%). Among those patients with OH, 10/17 (59%) patients had CI. In OH patients with CI, transient overdrive pacing upon standing maintained SBP and DBP as compared to baseline and prevented OH in the majority of patients (80%). By contrast, transient overdrive pacing in OH patients without CI had no significant effect on the decrease in SBP upon standing and prevented OH in only 20% of patients. CONCLUSIONS: OH is common (27%) in the elderly pacemaker population. In a subgroup of these patients, CI may be responsible for the occurrence of OH, and OH can be prevented by transient overdrive pacing upon standing.

Blood pressure response to transition from supine to standing posture using an orthostatic response algorithm.

Upon standing from a supine position, the normal response is an increase in heart rate to maintain blood pressure (BP). In patients with chronotropic incompetence, heart rate may not increase upon standing, and they may experience orthostatic hypotension (OH). We evaluated a new orthostatic response (OSR) pacing algorithm that uses an accelerometer signal to detect sudden activity following prolonged rest to trigger a 2 minutes increase in pacing rate to 94 bpm. Ten recipients of DDDR pacemakers which contain the OSR compensation algorithm (mean age = 77 +/- 9 years, 8 women) with sick sinus syndrome (n = 6) or atrioventricular block (n = 4) were studied. In all patients BP was measured before and 0.5, 1, 1.5, 2, and 3 minutes after standing at their programmed base rate. A 20 mmHg fall in systolic BP upon standing was observed in five patients (OH patients), while the other five were considered non-OH patients. The measurements were repeated with the OSR algorithm turned on. Mean BP was defined as 1/3 systolic BP + 2/3 diastolic BP. Baseline heart rate was significantly slower in OH patients (62 +/- 2 bpm) than non-OH patients (71 +/- 7 bpm, P < 0.05). In OH patients mean BP increased significantly upon standing (P < 0.05 for all comparisons) with the algorithm ON instead of decreasing with the algorithm OFF, at 1 minute (+3.4 vs -10.3 mmHg), 1.5 minutes (+7.0 vs -4.9 mmHg), 2 minutes (+1.6 vs -6.7 mmHg), and 3 minutes (+2.5 vs -8.5 mmHg). These preliminary results suggest that the OSR algorithm maintains BP upon standing in patients with OH.

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.

Impedance cardiography for atrioventricular interval optimization during permanent left ventricular pacing.

Left ventricular (LV) pacing is increasingly used in the management of congestive heart failure. Optimization of the atrioventricular (AV) interval is essential to maximize the hemodynamic benefits of this therapy. Although Doppler echocardiography (echo) is the most widely used method, it is time-consuming, expensive, and operator-dependent. We examined the value of an impedance cardiography (IC)-based method of cardiac output (CO) measurement to optimize the AV interval in 5 men and 1 woman (mean age = 72 +/- 11 years) during permanent LV pacing with a 4.8 Fr unipolar coronary sinus pacing lead. Simultaneous measurements of CO by IC and echo were performed at AV intervals of 50, 80, 110, 150, 180, and 225 ms during DDD pacing at 85 beats/min. The optimal AV interval varied between 110 and 180 ms. In 5 of 6 patients (83%), the optimal AV interval by echo and IC was identical. While CO measurements were higher with IC than with echo (6.1 +/- 0.4 L/min vs 4.7 +/- 0.3 L/min, P < 0.05), CO measurements by IC and echo were closely correlated r = 0.67, P < 0.001). In conclusion, our initial experience suggests that IC is a reliable method of AV interval optimization during LV pacing. IC and echo measurements of CO during LV pacing were closely correlated.

Functional abnormalities in patients with permanent right ventricular pacing: the effect of sites of electrical stimulation.

OBJECTIVES: We sought to evaluate the long-term effects of alternative right ventricular pacing sites on myocardial function and perfusion. BACKGROUND: Previous studies have demonstrated that asynchronous ventricular activation due to right ventricular apical (RVA) pacing alters regional myocardial perfusion and functions. METHODS: We randomized 24 patients with complete atrioventricular block to undergo permanent ventricular stimulation either at the RVA (n = 12) or right ventricular outflow (RVOT) (n = 12). All patients underwent dipyridamole thallium myocardial scintigraphy and radionuclide ventriculography at 6 and 18 months after pacemaker implantation. RESULTS: After pacing, the mean QRS duration was significantly longer during RVA pacing than during RVOT pacing (151 +/- 6 vs. 134 +/- 4 ms, p = 0.03). At six months, the incidence of myocardial perfusion defects (50% vs. 25%) and regional wall motion abnormalities (42% vs. 25%) and the left ventricular ejection fraction (LVEF) (55 +/- 3% vs. 55 +/- 1%) were similar during RVA pacing and RVOT pacing (p > 0.05). However, at 18 months, the incidence of myocardial perfusion defects (83% vs. 33%) and regional wall motion abnormalities (75% vs. 33%) were higher and LVEF (47 +/- 3 vs. 56 +/- 1%) was lower during RVA pacing than during RVOT pacing (all p < 0.05). Patients with RVA pacing had a significant increase in the incidence of myocardial perfusion defects (p < 0.05) and a decrease in LVEF (p < 0.01) between 6 and 18 months, but patients with RVOT pacing did not (p > 0.05). CONCLUSIONS: This study demonstrates that preserved synchronous ventricular activation with RVOT pacing prevents the long-term deleterious effects of RVA pacing on myocardial perfusion and function in patients implanted with a permanent pacemaker.