Theo van der Nagel

Acute and short-term effects of partial left ventriculectomy in dilated cardiomyopathy: assessment by pressure-volume loops.

OBJECTIVES The aim of this study was to evaluate the short-term effects of partial left ventriculectomy (PLV) on left ventricular (LV) pressure-volume (P-V) loops, wall stress, and the synchrony of LV segmental volume motions in patients with dilated cardiomyopathy. BACKGROUND Surgical LV volume reduction is under investigation as an alternative for, or bridge to, heart transplantation for patients with end-stage dilated cardiomyopathy. METHODS We measured P-V loops in eight patients with dilated cardiomyopathy before, during and two to five days after PLV. The conductance catheter technique was used to measure LV volume instantaneously. RESULTS The PLV reduced end-diastolic volume (EDV) acutely from 141+/-27 to 68+/-16 ml/m2 (p < 0.001) and to 65+/-6 ml/m2 (p < 0.001) at two to five days postoperation (post-op). Cardiac index (CI) increased from 1.5+/-0.5 to 2.6+/-0.6 l/min/m2 (p < 0.002) and was 1.8+/-0.3 l/min/m2 (NS) at two to five days post-op. The LV ejection fraction (EF) increased from 15+/-8% to 35+/-6% (p < 0.001) and to 26+/-3% (p < 0.003) at two to five days post-op. Tau decreased from 54+/-8 to 38+/-6 ms (p < 0.05) and was 38+/-5 ms (NS) at two to five days post-op. Peak wall stress decreased from 254+/-85 to 157+/-49 mm Hg (p < 0.001) and to 184+/-40 mm Hg (p < 0.003) two to five days post-op. The synchrony of LV segmental volume changes increased from 68+/-6% before PLV to 80+/-7% after surgery (p < 0.01) and was 73+/-4% (NS) at two to five days post-op. The LV synchrony index and CI showed a significant (p < 0.0001) correlation. CONCLUSIONS The acute decrease in LV volume in heart-failure patients following PLV resulted at short-term in unchanged SV, increases in LVEF, and decreases in peak wall stress. The increase in LV synchrony with PLV suggests that the transition to a more uniform LV contraction and relaxation pattern might be a rationale of the working mechanism of PLV.

Feasibility study of a fiber-optic system for invasive blood pressure measurements

A comparative study was conducted to evaluate the feasibility of a fiber‐optic sensor in invasive blood pressure measurements. Static and wide‐bandwidth stimuli were offered to the fiber‐optic, Millar, Baxter, and Sentron devices to measure static transfer function and transient response. Animal experiments focused on offset drift, dynamic accuracy, and electromagnetic sensitivity. Compared to the Millar, Sentron, and Baxter devices, the fiber‐optic sensor had a near‐identical static transfer function. Gain and offset errors were < 3.4% and < 0.25%, respectively. Hysteresis nonlinearity was < 0.1%. The dynamic accuracy of the fiber‐optic system matched that of the Millar and Sentron systems. Time delay was < 1 msec. Maximum rate of change was > 30,000 mm Hg/sec and bandwidth was 0–150 Hz minimum. Offset drift was 0.6 ± 0.03 mm Hg. Application of diathermy highlighted the fiber‐optic sensors excellent electromagnetic disturbance rejection. The fiber‐optic system appears to be a reliable, high‐fidelity pressure monitor in demanding clinical environments. Cathet Cardiovasc Intervent 2002;57:272–276.

Laboratory Performance Testing of Venous Cannulae During Inlet Obstruction

Venous cannulae undergo continuous improvements to achieve better and safer venous drainage. Several cannula tests have been reported, though cannula performance during inlet obstruction has never been a test criterion. In this study, five different cannulae for proximal venous drainage were tested in a mock circulation that enabled measurement of hydraulic conductance after inlet obstruction by vessel collapse. Values for hydraulic conductance ranged from 1.11 x 10(-2) L/min/mm Hg for a Thin-Flex Single Stage Venous Cannula with an open-end lighthouse tip to 1.55 x 10(-2) L/min/mm Hg for a DLP VAD Venous Cannula featuring a swirled tip profile, showing a difference that amounts to nearly 40% of the lowest conductance value. Excessive venous drainage results in potentially dangerous high-negative venous line pressures independent of cannula design. Cannulatip design featuring swirled and grooved tip structures increases drainage capacity and enhances cannula performance during inlet obstruction.

A New Stimulation Protocol for Cardiac Assist Using the Latissimus Dorsi Muscle

When treating severe cardiac failure with dynamic cordiomyoplasty, knowledge about the optimal way of stimulating the latissimus dorsi (LDJ muscie is of obvious importance. We evaluated a new stimulation protocol in/our goats using in situ electrical stimulation of the left LD muscle. Stimulation was started using a burst of two pulses with an interpulse interval of 100 msec for 50 bursts/min. The number of pulses was increased every 2 weeks concomitant with a decrease in interpulse interval. This resulted after 12 weeks in 60 bursts/min using bursts of six pulses with an interpulse interval of 20 msec after 12 weeks. Force measurements, which were done every 2 weeks, shoived an early decrease in contraction and relaxation speed as reflected in the ripple (= interstimulus amplitude/peak force amplitude measured at 10 HzJ. Fatigue resistance increased significantly within 4 weeks of conditioning as indicated by preservation of force, positive dF/dt, and negative dF/dt. Full preservation of these variables was seen even during a 1‐hour fatigue test at the end of the conditioning period. Skeletal muscle enzyme activity as an indicator of muscle domage showed a significont rise in creatine kinase enzyme activity only on the first day following the start of LD stimulation. LD muscle biopsies revealed almost complete transformation to type I muscle fibers with a significant increase in capillary/fiber ratio when compared to the nonsfimulated LD muscle. However, some biopsies, in particular near the electrodes, did show some signs of skeletal muscle damage. Contraction characteristics of the fully transformed LD muscles were tested by increasing the number of bursts of six pulses from 50/min to 100/min. Interpulse intervals of 20 and 33 msec were used. These tests revealed thaf maximal force, positive dF/dt, and negative dF/dt was reached with 50 bursts/min using a six pulse burst with interpulse intervals of 20 msec.