Shin Morita

Glucose-insulin-potassium solution improves left ventricular mechanics in diabetes

BACKGROUND The mechanism by which glucose-insulin-potassium solutions enhance recovery of left ventricular function after myocardial ischemia in diabetic patients is not well understood. We evaluated the effect of glucose-insulin-potassium on ventriculoarterial coupling and left ventricular mechanics in a chronic ovine model of diabetes. METHODS Diabetes was induced in 6 sheep with streptozotocin. After 6 months of diabetes, the response of the left ventricular pressure-volume relationship to 60 minutes of intravenous glucose-insulin-potassium solution (1,000 mL of 5% dextrose in water, 100 IU of regular insulin, 90 mmol of KCl at 1.5 mL x kg(-1) x h(-1)) was determined. RESULTS Glucose-insulin-potassium solution increased end-systolic elastance 68% (p = 0.01) and improved ventriculoarterial coupling (1.7+/-0.3 to 1.0+/-0.1; p < 0.01). Potential energy decreased 35% (p = 0.01), and pressure-volume area decreased 20% (p = 0.01). However, stroke work did not change; therefore stroke work efficiency increased from 50.1%+/-3.5% to 60.2%+/-5.1% (p = 0.01). CONCLUSIONS Glucose-insulin-potassium solution improves left ventricular contractility and ventriculoarterial coupling in diabetes. Left ventricular mechanics is improved by decreasing total mechanical work without significantly affecting stroke work, resulting in improved stroke work efficiency. Improved efficiency facilitates understanding of the enhanced tolerance to myocardial ischemia afforded by glucose-insulin-potassium solution.

Left ventricular oxygen utilization efficiency is impaired in chronic streptozotocin-diabetic sheep

OBJECTIVE Energy metabolism is altered in the diabetic heart. However, direct in vivo evidence that diabetes impairs energetics at the chamber level is lacking. Therefore, we investigated the effect of diabetes on left ventricular (LV) energetics in a chronic ovine model. METHODS Diabetes was induced in Merino-cross sheep with streptozotocin. Experiments were performed in five animals following 12 months untreated diabetes and six animals served as controls. Open-chest anesthetized sheep were instrumented to determine the LV pressure-volume relationship, oxygen consumption and free fatty acid uptake. RESULTS Diabetes impaired LV contractility (1.5+/-0.5 vs. 2.3+/-0.5 mmHg/ml, P<0.01). Stroke work was preserved but stroke work efficiency (stroke work/pressure-volume area) deteriorated (52+/-4 vs. 58+/-3%, P<0.01). Plasma free fatty acid levels increased (1885+/-1078 vs. 354+/-203 mmol/l, P<0.01) as did LV free fatty acid uptake (312+/-278 vs. 90+/-47 micromol/beat per 100 g LV, P=0.04). Contractile efficiency decreased (31.9+/-1.4 vs. 50.0+/-8.7%, P<0.01) while unloaded oxygen consumption did not change significantly. Therefore, LV oxygen utilization efficiency (stroke work/LV oxygen consumption) was compromised in the diabetic heart (14.9+/-2.8 vs. 24.3+/-4.0%, P<0.001). CONCLUSION This is the first study to demonstrate that diabetes alters ventricular energetics in vivo. LV oxygen utilization efficiency is impaired as a consequence of decreased contractile efficiency and stroke work efficiency. Impaired efficiency of oxygen utilization may explain in part the increased sensitivity of the diabetic heart to ischemia and the accelerated deterioration of ventricular function in diabetic patients.

HeartPatch implanted direct cardiac compression: effect on coronary flow and flow patterns in acute heart failure sheep.

A novel HeartPatch direct cardiac compression (DCC) device has been shown to effectively restore circulatory parameters in sheep with acute heart failure (HF). Its effect on the coronary circulation and myocardial perfusion, however, remains uncertain. The effect of DCC assist on coronary artery blood flow (CABF) and its patterns in acute HF sheep were examined in this study. Ten sheep (51 ± 6 kg) were implanted with a heart patch on each of the left ventricular and right ventricular free walls 1 week before study. Stable HF [cardiac output (CO) at 51 ± 8% of baseline] induced by intravenous esmolol resulted in CABF decreasing to 53 ± 16% of baseline (p < 0.001). DCC device activation did not alter CABF (54 ± 15% of baseline, N.S.) but was accompanied by increases in both peak antegrade and retrograde flow velocity (161 ± 75%, p < 0.001 and 413 ± 377%, p < 0.001). A shift in the proportion of flow occurring in diastole (%DF) also was observed: baseline, 81 ± 9%; HF, 82 ± 6%; DCC assist, 121 ± 16% (p < 0.001). Despite significant changes in coronary artery flow pattern resulting from DCC of the failing heart, total antegrade coronary flow was maintained. These findings suggest that myocardial perfusion is not compromised by DCC.

Effect of direct cardiac compression on left ventricular axial dynamics in sheep.

The HeartPatch direct cardiac compression device consists of two separate, nonsurround patches placed on the left and right ventricular free walls. Although the device has been shown to effectively restore circulatory parameters in acute heart failure sheep, the impact of device inflation on left ventricular geometry is yet to be elucidated. This study used sonomicrometer crystal transducers to examine three orthogonal left ventricular dimensions under various cardiac states and assessed the feasibility of determining stroke volume from these dimensions. Seven sheep (weight, 51 ± 5 kg) were implanted with six sonomicrometer crystals, and a heart patch was placed on each of the ventricles. The crystals were positioned to measure anterior-posterior, septal-lateral, and apex-base (long-axis) dimensions. Sheep were studied under both awake and anesthetized conditions. Septal-lateral shortening was increased with direct cardiac compression assist, whereas anterior-posterior and long-axis dimensions were either unchanged (awake) or decreased (anesthetized). Estimation of stroke volume, using the ellipsoid volume model, correlated well with stroke volume measured from an aortic flow probe; however, absolute stroke volumes were lacking in agreement.

Pneumopericardial tamponade in a patient with partial sternal dehiscence.

We present a rare case of sudden pneumopericardial tamponade in a patient with partial sternal dehiscence after cardiac surgery. Urgent decompression was needed in the management of the condition. Vacuum-assisted closure therapy was also used to prevent the problem from recurring. When there is acute hemodynamic deterioration in a patient with sternal wound dehiscence, pneumopericardial tamponade should be considered as a possible complication.