Biomedical subjects

A Liebrich

Publications and source records attributed to A Liebrich.

22 records · Page 2Linked to original sources

PubMed1995

Cardiac output in single-lead VDD pacing versus rate-matched VVIR pacing.

The importance of atrioventricular synchronous pacing compared with single-chamber rate-responsive pacing is still under discussion, especially for low-intensity workload representing daily life activities. We evaluated hemodynamics in single-lead VDD pacing versus VVIR pacing in 11 patients (8 men and 3 women, aged 58.6 +/- 13.8 years) with normal left ventricular function and a previously implanted single-lead VDDR pacemaker. A low-intensity steady-state treadmill test at 1 to 2.5 mph with a gradient of 2% to 4% was performed. Cardiac output was determined using a standard carbon dioxide rebreathing technique. Initially, the VDD mode was programmed, and after 5 minutes of exercise, cardiac output was measured in steady-state conditions. The pacemaker was then reprogrammed to the VVI mode at a rate 5 to 10 beats above the maximal atrial tracking rate to simulate rate-matched VVIR pacing (VVIRm). After 5 additional minutes of steady-state exercise, cardiac output was measured again. The maximal atrial rate in the VDD mode was 119 +/- 19 beats/min versus a programmed rate of 129 +/- 18 beats/min in the VVIRm mode. VDD pacing resulted in a significantly higher cardiac output than VVIRm pacing (10.6 +/- 1.9 vs 9.2 +/- 1.4 L/min; p < 0.002), with a mean difference of 1.6 +/- 1.2 L/min between the 2 modes. In the VDD mode, stroke volume (90.7 +/- 20.1 vs 71.6 +/- 13.0 ml; p < 0.001) and maximal oxygen uptake (1,183 +/- 264 vs 1,076 +/- 289 ml/min, p < 0.01) were also higher than in VVIRm.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Safety of antitachycardia pacing in patients with implantable cardioverter defibrillators and severely depressed left ventricular function.

The purpose of this study was to investigate the efficacy and safety of antitachycardia pacing (ATP) in third-generation implantable cardioverter defibrillators (ICDs) for terminating spontaneously occurring ventricular tachycardias (VTs) in patients with severely depressed left ventricular (LV) function. Ninety-one patients with active ATP were followed for 16 +/- 13 months. During this period, 775 VT episodes occurring in 36 patients were treated by ATP. The patients were divided into two groups according to their LV ejection fraction (LVEF): group A with LVEF < or = 30% (n = 20), and group B with LVEF > 30% (n = 16). There were no differences between both groups in age, gender, underlying heart disease, indication for ICD therapy, or drug therapy. The VT rates were comparable (group A: 183 +/- 16 beats/min; group B: 180 +/- 21 beats/min; P = NS). Eighty-three percent of all episodes (n = 332) in group A and 93% of the VTs (n = 443) in group B were ATP terminated (P < 0.01). Ten percent of VTs in group A were accelerated by ATP into the ventricular fibrillation zone versus 2% in group B (P < 0.01). The individual termination rate and acceleration rate per patient were comparable in both groups. All VT episodes unresponsive to ATP were converted by backup shocks. The efficacy of first-shock therapy was similar in both groups (group A: 89%; group B: 97%; P = NS). The proportion of patients who needed at least one backup shock for unsuccessful ATP was comparable in both groups (group A: 65%; group B: 56%; P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Defibrillators, Implantable↗

PubMed1993

Ventilation and heart rate response during exercise in normals: relevance for rate variable pacing.

The observation of a close relationship of heart rate to oxygen uptake (HR-VO2) and heart rate to minute ventilation (HR-VE) has been shown to be of particular value in rate variable pacing. However, the impact of anaerobic threshold (AT) for the HR-VO2 and HR-VE slope has been studied less. Twenty-three male and 16 female subjects, mean age 52 +/- 7 years, were selected in whom complete heart catherization and extensive noninvasive studies excluded major cardiopulmonary disease. Semisupine bicycle exercise testing with analysis of respiratory gas exchange was performed using a ramping work rate protocol with work increments of 20 watts/min. At the respiratory AT, determined by the V slope method, oxygen uptake (VO2-AT) was 15.2 +/- 3.0 mL/kg in males versus 13.8 +/- 2.3 mL/kg in females and heart rate (HR-AT) was 109 +/- 18 beats/min versus 119 +/- 20 beats/min, respectively. Heart rate was highly correlated (r > or = 0.9) to VO2 and minute ventilation (VE). A linear regression for HR-VO2, however, was found only in 16/39 and for HR-VE in 11/39 subjects. Assuming the AT as the breakpoint of two linear curves, it could be demonstrated that compared to low exercise HR appeared to increase at maximal exercise more in relation to VO2 but less in relation to VE; in men the individual slopes for HR-VO2 were 2.6 +/- 0.7 below but 3.2 +/- 1.0 above AT (P < 0.05) and the slopes for HR-VE were 1.6 +/- 0.5 below but 1.0 +/- 0.4 above AT (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Anaerobic Threshold↗

PubMed1992

Proof for piroximone's inotropic influence; can it safely be used in coronary artery disease? Analysis of end-systolic pressure-volume relations (conductance technique).

Improved contractility after applying piroximone (PIR) a new phosphodiesterase III inhibitor drug, is difficult to prove clinically. However, augmented contractility could increase the risk of myocardial ischemia when used in coronary artery disease (CAD). Analysis of the end-systolic pressure-volume relationship (ESPVR) as a load-independent parameter of the contractile left ventricular (LV) function allows for differentiation of PIR's effects: contractility vs. unloading. We therefore analyzed ESPVR and LV function in 16 CAD patients before and after PIR, 0.75 mg/kg intravenously. Emax increased by 39% (9/16 patients) and loops of the ESPVR (16 patients) moved leftward, indicating improved contractility. The difference in percent change PIR versus control (16 patients) demonstrated augmentation of LV function via unloading: LV volumes decreased (ESV by 37%, EDV by 19%), LV-filling pressure by 34%, and systemic vascular resistance by 19%; dP/dtmax increased by 28%, LV efficiency by 24%, cardiac index by 21%, and ejection fraction by 13%. Pacing-induced anginal threshold increased by 47% after PIR while the ischemic postpacing LV-filling pressure and ST-segment changes tended to normalize under the drug's influence. Thus, PIR improved LV function both by unloading and by positive inotropy. Lack of PIR-induced angina and an increased anginal threshold indicate that the drug can be used safely in CAD patients as well. The analysis of ESPVR proved to be safe and reliable in identifying contractility during the diagnostic cardiac catheterization routine.

Aged↗