摘要:

Synchronized coronary sinus retroperfusion (SCSR) with arterial blood has been extensively tested in animals. This intervention offers temporary support to areas of ischemic myocardium while a method of definitive revascularization is being sought. The feasibility and safety of this procedure for patients with unstable angina was therefore tested. A No. 7F autoinflatable retroperfusion balloon catheter (USCI) was inserted percutaneously into the coronary sinus of the study patients. Arterial blood was obtained through a No. 8F catheter placed in the femoral artery. Arterial blood was infused in a retrograde fashion into the coronary venous system during cardiac diastole by means of a piston-driven pump that was electrocardiographically synchronized with the drainage of the venous system during systole. This procedure was performed in five patients with unstable angina refractory to maximum medical therapy. SCSR significantly decreased the frequency of anginal episodes and the requirement for antianginal medications. SCSR also provided time for patient stabilization before diagnostic cardiac catheterization or therapeutic intervention. This preliminary experience suggests that synchronized coronary sinus retroperfusion is a feasible and safe procedure. It can be performed at the bedside with no apparent adverse effects to the patient. Retroperfusion also appears to be effective in relieving ischemic symptoms as assessed by clinical parameters. Based on our preliminary experience, further delineation of its clinical applications is warranted.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We have shown recently that tissue characterization of myocardium with ultrasound reflects changes associated with contractile function throughout the cardiac cycle. To determine whether ultrasonic tissue characterization can sensitively detect the impact of ischemic injury and reperfusion on contractile properties of the heart, we studied the time course of change of backscatter after 5, 20, and 60 min of coronary occlusion followed by reperfusion in 15 dogs. The time-averaged integrated backscatter (IB) and the amplitude and phase of cyclic variation of IB (phase relative to the left ventricular pressure waveform) were measured. A novel ultrasonic index of acute injury was identified, the phase-weighted amplitude of cyclic variation, and calculated by weighting the amplitude of cyclic variation of IB with respect to the phase. We hypothesized that backscatter variables would change dramatically after occlusion and that their restitution after reperfusion would sensitively reflect the extent and time course of reversibility of ischemic injury. After coronary occlusion, segmental wall thickening decreased from approximately 55% to 5% regardless of the duration of ischemia. Changes in backscatter associated with this decrease included an increase in time-averaged IB of approximately 5 dB, a 5 dB decrease in cyclic variation, an 80 degree phase shift, and a 7 dB decrease in phaseweighted amplitude. Wall thickening after reperfusion immediately after the 5, 20, or 60 min occlusions recovered to 45%, 27%, and 12% of baseline values, respectively. Within 3 hr it recovered to 53%, 44%, and 22%. Time-averaged IB recovered initially by 89%, 61%, and 44% (all p < .05) and continued to recover subsequently although more slowly. Ultimate recovery was virtually complete. In contrast to the rapid recovery of time-averaged IB, phase-weighted amplitude recovered initially to only 72%, 41%, and - 7% of baseline (all p < .05) and manifested slower and incomplete recovery when ischemia had been present for 20 or 60 min. After reperfusion, the time course of both cyclic variation and phase were reflected by changes in the phase-weighted amplitude. The backscatter variables assessed appear to sensitively delineate the duration, time course of recovery, and reversibility of ischemic injury in response to reperfusion. The results suggest that early recovery of timeaveraged IB corresponds in part to the restoration of tissue ultrastructural integrity. Accordingly, ultrasonic characterization of reperfused myocardium should be useful in defining the myocardium's response to reflow and to interventions such as thrombolysis designed to enhance salvage of ischemic myocardium.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

We studied the effects of ischemia on transmembrane action potentials, conduction time, and refractory periods of both endocardial and epicardial muscle cells of coronary-perfused cat left ventricles. Oxygenated Tyrode's solution was perfused through the left anterior descending coronary artery, while the preparation was superfused with Tyrode's solution gassed with 95% N2 and 5% CO2. Transmembrane action potentials recorded simultaneously from endocardial and epicardial cells were normal during coronary perfusion. When perfusion was discontinued (“ischemia”), rapid deterioration of action potentials and prolongation of conduction time were observed in both endocardial and epicardial cells. The magnitude of the reduction of action potential amplitude and action potential duration (APD), and of prolongation of conduction time, was greater in epicardial cells than in endocardial cells, although the change in resting membrane potential was almost the same. However, APD of endocardial cells decreased progressively during 30 min of ischemia, whereas APD of epicardial cells was reduced maximally at 10 min and then partially recovered. Shortening of refractory periods of endocardial cells paralleled APD shortening, whereas refractory periods of epicardial cells decreased for the first 10 min and then increased. At 10 min of ischemia, APD and refractory periods of epicardial cells were significantly shorter than those of endocardial cells. At 30 min of ischemia, refractory periods of epicardial cells exceeded those of endocardial cells because of development of greater postrepolarization refractoriness in epicardial cells. Accompanying these different changes in APD and refractory periods of endocardial and epicardial cells, spontaneous extrasystolic impulses increased and rapid runs of extrasystolic impulses could be induced by extrastimuli. Our data suggest that dispersion of repolarization and refractory period between endocardial and epicardial cells is related to the development of arrhythmias during early ischemia. In addition, heterogeneities of both the initial change in refractory period paralleling APD shortening and the late-developed postrepolarization refractoriness may be involved in the occurrence of acute ischemic arrhythmias.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

To determine whether chronic pressure overload and hypertrophy of the right ventricle alter the diastolic properties of the left ventricle, six adult dogs underwent banding of the pulmonary artery and were instrumented for studies 8 months later. Fourteen control dogs were also studied. Pressure and dimension data were collected from the dogs while they were awake and unsedated. The anterior-posterior, septal-free wall, and base-apex axis diameters of the left ventricle were measured with ultrasonic dimension transducers. Right and left ventricular pressures were measured with micromanometers. Pulmonary arterial banding resulted in increased right ventricular/body mass ratios (2.70 + 0.36 g/kg vs 1.52 + 0.15 g/kg control; p ' .05) and increased left ventricular/body mass ratios (4.84 ± 0.64 g/kg vs 4.21 ± 0.49 g/kg control; p ' .05). Right ventricular peak systolic and enddiastolic pressures were higher among the banded dogs (50 ± 20/7 + 5 mm Hg vs 31 + 6/3 ± 2 mm Hg control; p ' .05). A rearrangement in the three-dimensional geometry of diastolic filling occurred in the banded dogs. Extension from unstressed diastolic dimension (strain) in the base-apex axis was significantly larger in the banded dogs at left ventricular transmural pressures of 12, 8, and 4 mm Hg; strains in the septal-free wall axis were significantly smaller at transmural pressures of 12 and 8 mm Hg. Normalized diastolic left ventricular pressure-volume data and midwall circumferential stressstrain data were fit to the Kelvin viscoelastic equation. The normalized pressure-volume relationships of the banded dogs lay significantly to the left of those of the controls, indicating a loss of left ventricular chamber compliance. The midwall circumferential stress-strain relationships of the banded dogs were also shifted to the left, indicating a loss of intrinsic myocardial compliance. Thus, during the course of right ventricular hypertrophy caused by right ventricular pressure overload, alterations in the mass, geometry, and material properties of the left ventricle occur. At 8 months the chamber compliance of the left ventricle is compromised by these changes.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

To examine whether nicardipine, a dihydropyridine derivative, limits size of myocardial infarction, and to compare the protective effects of nicardipine administered before and early and late after coronary artery occlusion, 99mTc-labeled albumin microspheres were injected into the left atrium during 5 min temporary coronary artery occlusion to determine the extent of the hypoperfused zone (the area at risk). The coronary arteries were then reperfused for 45 min before 6 hr permanent coronary artery occlusion. Fifteen minutes before permanent occlusion, dogs were randomly assigned to (1) a control group (n = 11), (2) a pretreatment group (n = 9), which received at this point 10, μg/kg of nicardipine as a loading dose followed by a continuous infusion of 8 p.g/kg/hr for 6 hr, (3) an early treatment group (n = 9), in which nicardipine treatment was initiated 15 min after occlusion, or (4) a late treatment group (n = 8), in which nicardipine administration was delayed for 3 hr. Six hours after coronary artery occlusion, the hearts were excised and the left ventricle of each was cut into 3 mm thick slices and stained with triphenyltetrazolium chloride. The extent of myocardial necrosis was measured by planimetry of the unstained areas. Thereafter, the same slices were autoradiographed and the extent of the hypoperfused zone was measured by planimetry of the “cold spot.” The extent of the hypoperfused zone was identical among the four groups. In the control group, the ratio of the extent of myocardial necrosis to the extent of the hypoperfused zone was 95.8 3.8% (mean SEM). However, it was significantly smaller in the pretreatment group (59.9 + 13.3%, p < .05) and the early treatment group (49.0 + 10.6%, p < .01) than in the control group. In the late treatment group, this value was not different from that in the control group (86.5 + 7.1%). There was a close inverse correlation between reduction of infarct size and the extent of the hypoperfused zone in the pretreatment and early treatment groups. Thus, nicardipine administered before or early after coronary artery occlusion limited infarct size by 37% to 49%, whereas when administration was delayed for 3 hr infarct size was not reduced. Furthermore, nicardipine had more striking effects on the ischemic myocardium of dogs with small hypoperfused zones than on that of dogs with large hypoperfused zones.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

摘要:

The response to exercise was investigated in trained and sedentary rats with moderate compensated heart failure produced by myocardial infarction (MI) and in rats that underwent sham operations. Trained rats ran on a treadmill (10% grade at 20 m/min) for 60 min/day, 5 days/week for 10 to 12 weeks, whereas sedentary rats had only limited activity. Maximal oxygen consumption normalized for body weight (ml kg min `) was determined for each rat and found to be (1) greater in trained rats when compared with sedentary rats and (2) greater in sham-operated rats when compared with their counterparts that suffered infarction. In addition, skeletal muscle succinate dehydrogenase activities were greater and the blood lactic acid response to submaximal exercise was lower in trained rats compared with sedentary rats. Left ventricular infarct size for sedentary and trained rats with infarction was 36 3% and 34 + 3% of the total endocardial circumference, respectively, and resulted in (1) elevated left ventricular end-diastolic pressures at rest and during exercise, (2) lower mean arterial pressures at rest, and (3) lower maximal heart rates when compared with those in their sham-operated counterparts. However, normalization of mean arterial pressures during submaximal and maximal exercise was found along with a trend toward normalization of maximal heart rate when trained rats with infarction were compared with their sedentary counterparts. Blood flows to the kidneys, organs of the gut, and skeletal muscle during both submaximal and maximal exercise were unaffected by either myocardial infarction or training; no differences between sedentary and trained rats with infarction and sedentary and trained sham-operated rats were found. These results demonstrate that an exercise training program of moderate intensity produces beneficial hemodynamic and metabolic effects in rats with moderate compensated heart failure.

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID

ISSN:0009-7322    

出版商:OVID    

年代:1986

数据来源: OVID