C1-INH and its Effect on Infarct Size and Ventricular Function in an Acute Pig Model of Infarction, Cardiopulmonary Bypass, and Reperfusion

BACKGROUND

Recent studies suggest that complement inhibition reduces reperfusion injury. A clinical setting with local application of a C1 esterase inhibitor (C1-INH) has been modeled in an animal study in order to further investigate these findings.

METHODS

In 21 pigs, the left anterior descending coronary artery (LAD) was occluded distally to the first diagonal branch for 2 hours (h), including 1 h of cardioplegic arrest during CPB. After release of the coronary snare, C1-INH or NaCl (control) was applied to the aortic root. Thereafter, the aortic cross-clamp was removed and the heart was reperfused for 30 minutes before weaning from CPB. Left ventricular pressure volume analysis was performed by a multielectrode conductance catheter and the area at risk and infarct size were determined from excised hearts.

RESULTS

The following data were observed (mean+/-SEM) for the control group and the C1-INH group, respectively, after 1-h ligation of the LAD: heart rate (HR) 86+/-3 and 93+/-6 beats/min, stroke volume (SV) 1.2+/-0.1 and 1.2+/-0.1 ml/kg, aortic pressure (AoP) 83+/-6 and 87+/-5 mmHg, left ventricular end-diastolic pressure (LVedP) 12+/-1 and 11+/-2 mmHg; two hours after weaning from CPB: HR 106+/-9 and 123+/-4 beats/min, SV 0.9+/-0.1 and 0.9+/-0.1 ml/kg, AoP 65+/-5 and 79+/-7 mmHg, LVedP 9+/-1 and 8+/-1 mmHg. Conductance catheter measurements showed no improved left ventricular performance after C1-INH application. Infarct size to area at risk ratio was 61.5+/-4.2% for controls and 61.4+/-4.8% for C1-INH.

CONCLUSIONS

Intracoronary application of complement inhibitor in an acute infarction model, which mimicked a clinical setting of urgent coronary bypass grafting after ischemia, has been shown to neither influence the area of infarction, nor the ventricular function.

Diastolic Unloading and Improved LV Pump Efficiency Early After Repair of the Insufficient Mitral Valve

BACKGROUND

This study aimed to evaluate the acute effect of mitral valve repair (MVR) on LV hemodynamics and geometry in patients with normal ventricular function.

METHODS

In 10 patients with severe mitral regurgitation undergoing MVR, pressure-volume relationships were recorded before annuloplasty prior to and after hemodilution and after MVR during stable circulatory condition, using the conductance catheter technique (CC). Analyses were done off-line; volume calibration was based on data obtained after completion of valve repair (mean +/- s.d.).

RESULTS

CC showed that only 61 +/- 15 % of left ventricular output was ejected into the systemic circulation, regurgitation volume being 39 +/- 15 %. MVR led to a reduction in LV stroke work index from 4.7 +/- 1.8 mm Hg x l x m (-2) at before valve repair to 2.2 +/- 1.0 mm Hg x l x m (-2) after surgery at unchanged cardiac index. LV diastolic filling parameters improved: LV relaxation time constant tau decreased from 52 +/- 15 to 37 +/- 11 ms and dP/dt (min) increased from - 873 +/- 231 to - 1286 +/- 283 mm Hg x s (-1).

CONCLUSIONS

Despite cardioplegic arrest, MVR leads to acute improvement of diastolic LV function early after the operation. This may explain why valve repair has an acute positive effect in patients with impaired LV function.

Effect of cardiopulmonary bypass and hemofiltration on plasma cytokines and protein leakage in pigs

BACKGROUND

The hypothesis that an inflammatory process during and after cardiopulmonary bypass (CPB) impairs hemodynamics and causes increased capillary protein leakage and that this is possibly ameliorated by hemofiltration (HF) was tested.

METHOD

26 anesthetized pigs were subjected to 120 min CPB (90 min cardioplegia followed by 30 min reperfusion, combined with conventional and modified HF in 13 animals). Hemodynamics, leukocytes, cytokines (IL-1ra, IL-8, IL-10, TNF-alpha), LNPI, plasma protein, and the half-life of i.v. injected Evans Blue (t/2) were assessed before and after CPB.

RESULTS

CPB was followed by depression of left ventricular function and activation of inflammatory mediators. Although a slight elimination of some inflammatory mediators occurred, HF did neither improve cardiac function nor reduce the inflammatory process. Plasma protein was lost during CPB and hemofiltration by protein trapping to the surfaces of the CPB system, by filtration across the hemofilter, and by increased microvascular filtration (solvent drag). The latter was probably due to an increased filtration pressure in consequence of the reduction of plasma colloid osmotic pressure by the crystalloid primed CPB. t/2 did not indicate an increased microvascular protein leakage after CPB.

CONCLUSION

Hemofiltration is ineffective in improving cardiac function or reducing the inflammatory response of CPB in the pig model.

Pulmonary function after biventricular bypass for autologous lung oxygenation

OBJECTIVE

Biventricular bypass (BVB) with autologous lung perfusion is an attractive concept to ameliorate systemic inflammatory response by eliminating the oxygenator from the extracorporeal circulation. The effect of biventricular bypass as compared to heart-lung bypass (HLB) on pulmonary function parameters was therefore studied in an experimental model.

METHODS

Heart-lung bypass using a membrane oxygenator or biventricular bypass using the autologous lung for gas exchange was performed for 120 min in an alternating series of 12 mongrel dogs with the heart arrested for 90 min by crystalloid cardioplegia and 30 min reperfusion, followed by a 120 min observation period. Systemic (CO, SVR) and pulmonary hemodynamics (PVR), extravascular lung water (EVLW, double indicator), gas exchange (FiO(2), PaO(2), PaCO(2)), lung compliance (PC), and ventilation (RMV) at FiO(2)=0.5 required to maintain PaCO(2) at 40 mmHg, were measured. Blood cell counts (Leuco, Thrombo) were performed.

RESULTS

All animals were weaned from extracorporeal circulation without inotropes, no differences were observed in cardiac output and blood pressures. The following data were obtained in % change from pre-bypass values 60 min after extracorporeal circulation (*:P<0.05, HLB vs. BVB): PVR, +108 vs. +45*; EVLW, +21 vs. -2*; PC, -12 vs. +4*; PaO(2), -8 vs. +21; RMV, +21 vs. +2*; Leuco, -65 vs. -12*; Thrombo, -62 vs. -35*.

CONCLUSION

During and after heart-lung bypass the lung is subject to severe ischemia-reperfusion injury as indicated by edema, cell trapping, and impaired gas exchange. The data demonstrate superior preservation of pulmonary mechanics and function after biventricular bypass as compared to heart-lung bypass and support the clinical strategy of using biventricular bypass in patients with impaired lung function.

Effect on coronary artery flow reserve and resistance in the remote area after acute coronary artery occlusion in the pig model

BACKGROUND

It has been reported that vasodilator function in remote myocardial regions supplied by "angiographically normal" coronary arteries is impaired in patients after acute myocardial infarction (MI). The aim of this study was to determine whether coronary artery flow reserve and coronary artery resistance in remote, nonischemic areas are also altered in experimental MI.

METHODS

Experiments were performed in anesthetized pigs. In group 1 infarction was induced by ligation of the left-anterior descending artery (LAD); group 2 consisted of sham-operated animals. Hemodynamic parameters, coronary artery resistance, and myocardial blood flow (MBF) were measured before and 4 hours after MI under rest and during infusion of adenosine.

RESULTS

Coronary artery dilation by adenosine caused a similar increase in MBF before and 4 hours after coronary artery occlusion. Resting MBF after acute MI was not altered, although a significant reduction (15%; P < .04) in mean aortic pressure was observed compared with baseline. Coronary artery resistance was significantly reduced by adenosine (P < .04) before MI, as well as at 4 hours after MI (P < .03). Coronary artery flow reserve was not adversely affected. The sham-operated animals showed similar results without any significant differences between the two study groups.

CONCLUSION

This study indicates that an acute MI in pigs did not increase coronary artery resistance in the remote area after MI and therefore did not adversely affect coronary artery flow reserve in the nonischemic vascular bed. Further studies are necessary to fully understand the exact mechanism of the alterations in remote flow reserve of patients after MI.

Spectrotemporal mapping of high-resolution ECGs in experimental myocardial infarction: comparison with time-domain analysis and epicardial electrograms

The study was undertaken to evaluate the relationship of signal-averaged ECG (SA-ECG) readings in the frequency domain (STM) and epicardial electrograms (EE) recorded before and after acute myocardial infarction (AMI) in pigs and to compare the changes with findings in time-domain analysis (TDA). In 20 pigs the left anterior descending artery (LAD) was ligated. Prior to ligation, a SA-ECG was recorded (method of Simson) and bipolar electrodes were used to register EE in the areas supplied by the LAD and the circumflex artery (CIRC). Five minutes after LAD ligation, all measurements were repeated. Time-domain parameters were QRS duration (QRS D) and the duration of the signal below 30 microV (LAS 30). Beginning at a point of 20 ms before the QRS end, the frequency spectra (0-200 Hz) of 25 segments of 80-ms duration at the QRS end were analyzed. The volumes below the 25 curves were analyzed separately for 0-50 Hz, 51-100 Hz, 101-150 Hz, and 151-200 Hz. After AMI, five pigs died within 7 minutes. In 15 pigs, QRS D as well as LAS 30 lengthened significantly (P<0.05; P<0.001). Spectrotemporal mapping (STM) showed a significant decrease of the frequencies above 50 Hz (51-200 Hz) in the entire group and in the animals with late potentials (P<0.05). EE of the LAD area were significantly prolonged (P<0.01); this did not correlate with the changes in STM parameters. In pigs acute myocardial infarction causes a shift towards lower frequencies in the STM which most likely reflects the slowed depolarisation in the ischemic area.

Effect of dopamine and atrial pacing on stunned myocardium

OBJECTIVE

Post-ischaemic stunned myocardium shows an impaired function at restored coronary blood flow, but performance can be normalized by positive inotropic stimulation. The power of stunned myocardium, however, is not augmented with increasing heart rate by atrial pacing, which is in contrast to intact areas. This pathological response is mitigated by inhibiting the degradation of cyclic AMP. The present experiments studied the effect of stimulating cyclic AMP formation by dopamine on the response of stunned myocardium to atrial pacing.

METHODS

In anaesthetized (piritramide) open chest pigs, heart rate, left ventricular and aortic pressure, left descending (LAD) and circumflex (LCX) coronary artery and aortic blood flow, myocardial systolic shortening in the LAD and LCX area were monitored, and myocardial power was calculated. The LAD region was subjected to ischaemia and reperfused for 2 h. Subsequently, heart rate was raised by right atrial pacing before and during intravenous infusion of dopamine (10 microg/kg per min). The ischaemic/reperfused area was sliced post mortem and stained by triphenyl tetrazolium chloride to exclude myocardial infarction. Data from 11 experiments are presented.

RESULTS

After 2 h LAD reperfusion, LAD blood flow and power were 100% and 36% of pre-ischaemic control, respectively, indicating myocardial stunning. The power of the intact area was not changed significantly (111% of control). Increasing heart rate by +36 and +70 from 94 beats/min increased the power of the intact area to 161% and 183% of control; the power of the stunned myocardium decreased to 34% and 19% of pre-stunning control. Dopamine increased the power of the stunned region to 143% of the pre-stunning level and the power of the intact area to 206% of control. Increasing heart rate by +34 and +70 from 113 beats/min during dopamine, increased the power of the intact myocardium to 288% and 344% of control and the power of the stunned region to 177% and 174% of the pre-stunning level.

CONCLUSIONS

The data confirm the pathological response of stunned myocardium to atrial pacing and the recruitment of a functional reserve by catecholamines. The adverse effect of pacing on the function of stunned myocardium is abolished by positive inotropic stimulation. Possibly, the cyclic AMP system is involved in the normal response to pacing and this pathway is disturbed in stunned myocardium; other defects are not excluded or supported, however. Physiologically increased heart rate by an increased activity of the sympathetic nervous system, is probably not accompanied by a reduced power of stunned myocardium, due to the associated positive inotropic stimulation.

Effect of milrinone and atrial pacing on stunned myocardium

OBJECTIVE

Most mammalian cardiac muscles show a positive force-frequency relation, which is turned into a negative relation in failing hearts. Stunned myocardium shows similar defects as failing myocardium, it has a functional reserve recruitable by positive inotropic interventions, and possibly shows a disturbed response to increased heart rate. The present experiments compare in vivo the response of stunned and intact myocardium to atrial pacing before and during inotropic stimulation by milrinone.

METHODS

In anaesthetised (piritramide) open chest pigs, heart rate, left ventricular and aortic pressure, left descending (LAD) and circumflex (LCX) coronary artery and aortic blood flow, myocardial systolic shortening in the LAD and LCX area were monitored, and myocardial power was calculated. The LAD region was subjected to ischaemia and reperfused. Heart rate was raised by right atrial pacing after 90 min reperfusion before and during i.v. milrinone (105 microg/kg bolus + 8 microg/kg per min infusion). The ischaemic/reperfused area was sliced post mortem and stained by triphenyl tetrazolium chloride to exclude myocardial infarction. Data from ten experiments are presented.

RESULTS

After 90 min LAD reperfusion, LAD blood flow and power were 110 and 36% of preischaemic control, respectively, indicating myocardial stunning. The power of the intact area was not changed (102% of control). Pacing from 87 to 164 per min increased the power of the intact area (+96%), the power of the stunned myocardium decreased (-64%). Milrinone increased the power of the stunned region to 72% of the pre-stunning level and the power of the intact area by +51%. Pacing from 111 to 164 per min during milrinone increased the power of the intact myocardium to the same level as before milrinone, the power of the stunned region did not change.

CONCLUSIONS

Stunned myocardium responds pathologically to atrial pacing with a negative staircase in contrast to the positive staircase of intact myocardium. Inotropic stimulation by the phosphodiesterase inhibitor milrinone recruited the functional reserve of stunned myocardium. Milrinone did not restore a positive staircase in stunned myocardium, but power was maintained during atrial pacing. The pathological staircase of stunned myocardium may arise from an impaired availability of cyclic AMP, but the data do not exclude defects in calcium handling, a dysfunction of the sarcoplasmic reticulum, or an impaired Ca-sensitivity of the myofilaments.

[Experimental principles for preserving annulo-ventricular integrity of the mitral valve]

Despite numerous improvement in cardiac surgery the results in mitral valve replacement are still not satisfactory, since impaired left ventricular function continues to be a problem during the postoperative course. In order to investigate the effect of mitral valve replacement on left ventricular function canine experiments were performed: During extracorporeal circulation bileaflet mitral valve prostheses were implanted preserving the ventriculo-annular continuity. Flexible wires were slung around the chordae of the subvalvular mitral apparatus and brought to the outside through the left ventricular wall. Left ventricular diameters were measured by sonomicrometry, left ventricular stroke volume, left ventricular enddiastolic volume and ejection fraction by dye dilution technique as well as left ventricular and aortic pressure by catheter tip manometers. After finishing cardiopulmonary bypass control values were registered and different preload values achieved by volume loading with blood transfusions to left ventricular enddiastolic pressures of 12 mm Hg. Subsequently under normovolumic conditions the chordae tendineae of the anterior and posterior papillary muscles of the mitral valve were cut from the outside, while the heart was beating, by application of electrocautery on the steel wires. Following severance of the ventriculo-annular continuity of the mitral valve again function curves of left ventricular hemodynamics were made during volume transfusions. When the chordae had been divided the left ventricular enddiastolic diameter increased by 10% in the major axis, while in the minor axis no significant changes occurred. The systolic shortening was impaired substantially by reduction of 43% during the ejection phase when the subvalvular mitral apparatus had been severed. Left ventricular enddiastolic volume was increased by 18% at any preload level, while left ventricular ejection fraction was reduced by 16%. Consequently left ventricular stroke volume was decreased by 24% at any left ventricular enddiastolic volume, when the chordae had been divided. It can be concluded that left ventricular geometry is changed when the annulo-ventricular continuity has been interrupted at mitral valve replacement: The major axis of the left ventricle is increased and the enddiastolic volume is augmented. The left ventricle is only able to eject the same stroke volume at higher preload levels when the chordae tendineae have been divided. The same cardiac performance can only be achieved by volume loading and at the expense of higher wall tension, which leads to unfavorable conditions in terms of cardiac muscle mechanics with reduced exercise tolerance. These data speak for preservation of the annulo-ventricular continuity in mitral valve replacement. Provided that these results from acute canine experiments can be transferred to humans, one would suggest that preservation of the mitral subvalvular apparatus is of importance in patients with dilated hearts and with impaired left ventricular function.

Bi-ventricular function assessed intraoperatively before and after anatomical correction of transposition of the great arteries

After anatomical correction of transposition of the great arteries (TGA), the left ventricle (LV) is forced to develop systemic pressures without having had time for adaptation. Thus, one might expect dilatation of the LV at least in the very early intraoperative period following the operation. In nine patients with TGA aged 8-24 days (median 9.5 days) which were selected for arterial switch operation (ASO), Dacron-patch mounted thin piezoceramic transducers were attached intraoperatively by fibrin glue to opposite epicardial surfaces of the right (RV) and/or LV for continuous assessment of external minor diameters (RVD, LVD; sonomicrometry) before and after correction. Right and left ventricular pressures (RVP, LVP) were measured simultaneously and pressure-diameter loops were generated. Right and left ventricular power indices (RVPi, LVPi: = HRxVPxVsD) was calculated from heart rate, ventricular pressures, and systolic shortening of the respective ventricular diameter (RVsD, LVsD). Data obtained during circulatory steady-state immediately before extra-corporeal circulation (ECC) and up to 45 min after ECC were compared. By avoiding volume overload (CVP < or = 10 mmHg) at weaning off ECC and by lowering the systemic vascular resistance and, thus, LV afterload (approximately 8 micrograms.kg-1 min-1 dobutamine), the LV developed systemic pressure (70 +/- 7 vs. 41 +/- 4 mmHg) at unchanged diastolic LV end-diastolic pressure (LVedP) (10 +/- 3 mmHg). Left ventricular power index increased by 45 +/- 25%, although the extent of systolic shortening of LVD was reduced by 20 +/- 10%. Simultaneously, the RV was effectively unloaded (RVedP: 8 +/- 3 vs 11 +/- 6 mmHg; RVP: 39 +/- 7 vs 53 +/- 9 mmHg; RVPi: -42 +/- 27%).(ABSTRACT TRUNCATED AT 250 WORDS)

Reservoir characteristics of Mainz pouch studied in animal model. Osmolality of filling solution and effect of oxybutynin

In a canine model of the Mainz pouch, intracavitary pressure and compliance were measured during instillation of isosmotic and hyperosmotic (900 mmol/kg water) solutions of saline. Wall properties of small- and large-bowel segments of the pouch were assessed individually by sonomicrometry. Intraluminal pressures increased more steeply during filling with hyperosmotic solution, resulting in reduced distensibility of small- and large-bowel segments. Additionally, instillation of the hyperosmotic solution resulted in increased amplitudes and frequency of intracavitary pressure waves. The results indicate that this was the result of a combination of intensified bowel contractions and an increased mural tension. Topical application of oxybutynin abolished these effects. These findings are reviewed in light of the nocturnal increase in urine osmolality, its correlation with nocturnal incontinence in patients with enterocystoplasty, and possible treatment choices.

Importance of the left ventricular subvalvular apparatus for cardiac performance

The importance of the subvalvular mitral apparatus for left ventricular performance was studied in eight anesthetized dogs. During extracorporeal circulation St. Jude Medical mitral valve prostheses were implanted preserving the chordae tendineae. Flexible wires were slung around the chordae tendineae and brought to the outside through the left ventricular wall to cut the chordae tendineae by electrocautery in the closed beating heart. The left ventricular diameters were measured by sonomicrometry, left ventricular stroke volume and enddiastolic volume by dye dilution, and left ventricular pressure by catheter tip manometer. Data were collected at different preloads achieved by volume loading with blood before and after the chordae tendineae were cut. The results showed that after the chordae tendineae had been cut left ventricular systolic pressure, heart rate, diastolic and systolic diameters of the left ventricle along the minor axis were not different from the pre-cut values at any left ventricular enddiastolic pressure. However, significant differences were observed for maximum dp/dt (-15%), major axis diastolic diameter (+10%) and systolic shortening (-40%), enddiastolic volume (+18%) at any left ventricular enddiastolic pressure, and stroke volume (-24%) at any enddiastolic volume level. The data demonstrate that the subvalvular apparatus not only maintains physiologic valve function, but contributes significantly to left ventricular performance. The impairment of left ventricular function following removal of the subvalvular apparatus might be aggravated in pre-injured hearts in mitral valve disease. Consequently, the subvalvular apparatus should be preserved in mitral valve replacement whenever possible.

Experience with anatomical correction of transposition of the great arteries (TGA)

During the past seven years, 102 patients with TGA have been operated on using the switch operation. Overall early mortality was 5.9%, late mortality 2.%. Sixty-three newborns had an intact septum and were corrected between the 3th and 35th day after birth, 39 had a ventricular septal defect and/or associated anomalies. All operations were carried out under ECC and deep hypothermia. Myocardial function was recorded intraoperatively by using sonomicrometry. The data demonstrate that adaptation of the left ventricle to the new load conditions should be supported by drugs providing inotropic stimulation and afterload reduction. Mean follow-up time is 32.5 months, no rhythm problems have been recorded during that period, a few children revealed trivial pulmonary or aortic valve stenosis and/or incompetence. The switch operation permits good early results for newborns with TGA and intact septum and TGA with VSD. A decade has to pass in order to judge the long-term results.

Effect of the 'specific bradycardic agent' alinidine on the function of ischemic myocardium

In patients with coronary artery disease, the reduction of heart rate (HR) by beta-blockers can further impair myocardial function by reducing the contractility and coronary perfusion. This is possibly not the case for "specific bradycardic agents" like alinidine (ALI). The effect of ALI on ischemic myocardium, therefore, was studied in anesthetized open-chest dogs measuring left ventricular end-diastolic pressure (LVedP), dP/dt, aortic pressure (AoP) by catheter tip manometers, coronary blood flow (Q) electromagnetically, end-diastolic length (edL) and systolic shortening (sdL in %edL) of ischemic (RISC) and non-ischemic (NISC) wall segments by sonomicrometry. Group A (n = 11): Left coronary artery constriction to reduce Q (-53%) and poststenotic sdL (-54%), then i.v. injection of ALI (0.25 + 0.25 + 0.5 + 1.0 mg/kg), thereafter atrial pacing at HR before ALI. Group B (n = 9): Installation of an aorto-coronary bypass, pump-perfused at 50% of free flow, infusion of ALI into the bypass. The results showed that ALI iv dose-dependently reduced HR from 135/min to 90/min, LVedP rose from 8.6 to 10.0 mmHg and NISC-edL from 14.1 to 14.6 mm indicating increased ventricular filling. Non-ischemic systolic shortening did not change. Ischemic systolic shortening was improved from 9.2% to 17.5%, which was not due to an increase in RISC-edL (14.8 versus 14.7 mm), enhanced RISC-Q (13 versus 12 ml/min), reduced AoP (86 versus 84 mmHg) or change in inotropy (dP/dtmax: 2290 versus 2240 mmhg/s), but the increase in RISC-sdl correlated closely (r greater than 0.85) to the reduction in HR (oxygen-demand).(ABSTRACT TRUNCATED AT 250 WORDS)

Cyclic motion of ischemic ventricular wall area and hydrodynamics of the blood during ejection

Analysis of dimensional changes of ischemic left ventricular wall segments evidenced a dilation immediately after onset of ejection; thereafter, contraction appears delayed but almost regular. This biphasic systolic wall motion was correlated in a retrospective study to parameters indicating local intramural disorders, intraventricular load changes, and hydrodynamics of the blood during ejection. Hemodynamic data stored on a 16-track tape recorder were analyzed from 12 consecutive experiments in anesthetized dogs in which the left circumflex coronary artery (LCX) was gradually narrowed (coronary flow restriction greater than or equal to 50%). Left ventricular and aortic pressure, aortic blood velocity (v), acceleration/deceleration (dv/dt), and instantaneous stroke volume (m = integral of v*dt), and segment lengths of normal and ischemic myocardial regions (sonomicrometry) were numerically evaluated with 5 msec resolution. Systolic shortening of the intact myocardium correlates with the diminution of the intraventricular volume during ejection (r greater than 0.98). In contrast, ischemic segments dilate early during systole when the blood is accelerated; the extent of dilation depends on the degree of coronary flow reduction. The time course of lengthening coincides with the development of force F = m*dv/dt (r greater than 0.90) originating from regularly contracting parts of the ventricle. During blood deceleration, ischemic wall segments shorten as F turns to negative (r greater than 0.95). Thus, the wall motion of ischemic myocardial regions is modulated by the hydrodynamic force resulting from acceleration and deceleration of blood consecutively impeding and supporting the systolic function of the ischemic myocardium in the course of ejection.

Relation between epicardial electrograms and signal-averaged electrocardiograms after acute myocardial infarction in dogs

Signal-averaged electrocardiograms allow the non-invasive detection of late potentials which represent locally delayed conduction in the myocardium. To validate this method, it is necessary to compare the signal-averaged data with electrograms recorded directly from the heart. However, the studies performed to date involve only a consecutive collection of the invasively and non-invasively obtained data. To obtain a more direct comparison, we examined this relation at operation by simultaneous epicardial and signal-averaged measurements. Acute infarction in animals was chosen, because the ischemic area is a zone of delayed conduction whose presence can be verified in a signal-averaged electrocardiogram. For this purpose, the left anterior descending artery, proximal of large septal and diagonal branches, was tied off in nine mongrel dogs after thoracotomy. Before infarction, a signal-averaged electrocardiogram was recorded from the body surface. At the same time, epicardial electrograms were performed using bipolar electrodes both from the supply area of the left anterior descending artery and from that of the circumflex artery. Five minutes after coronary ligation, both the epicardial measurements and the signal-averaged electrocardiogram were repeated on the open thorax. Before occlusion of the left anterior descending artery, narrow activation complexes occurred in general in the epicardial electrograms and no late potentials were recorded in any dog by the signal-averaged electrocardiogram. Five minutes after coronary ligation, fractionated and prolonged electrograms occurred in the epicardial recordings from the ischemic zone, while the activation complexes in the uninfarcted supply area of the circumflex artery remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Significance of the subvalvular apparatus for left-ventricular dimensions and systolic function: experimental replacement of the mitral valve

To study the significance of the subvalvular apparatus for left-ventricular performance in mitral valve replacement, a new experimental model was developed. In 21 dogs St. Jude prostheses were implanted in the mitral position preserving the chordae tendineae and the papillary muscles by plicating and fixing the mitral leaflets with the prosthesis on the valvular annulus. Flexible steel wires were slung around the chordae tendineae of the anterior and the posterior papillary muscle separately and passed through the left ventricular wall via insulating plastic cannulas. Left-ventricular dimensions and global systolic function were measured during volume loading with blood before and after severance of the chordae tendineae by external application of electrocautery to the steel wires. Thus the heart continued beating without any interference following loss of the subvalvular apparatus. The external left ventricular diameters in the major and minor axis were determined by sonomicrometry. Left-ventricular systolic and diastolic pressures were measured by catheter tip manometers, stroke volume by electromagnetic measurements of flow in the ascending aorta. When the chordae tendineae had been cut, left-ventricular end-diastolic diameters in the major axis were increased ( + 2%), in the minor axis decreased (-1%) at any left-ventricular end-diastolic pressure. Systolic shortening of the major axis diameter was considerably reduced (20-27%) at any left-ventricular end-diastolic pressure following severance of the chordae tendineae. Significant increase of the systolic shortening in the minor axis diameter occurred at preload levels of 3-6 mmHg (15-8%), while at higher left-ventricular end-diastolic pressure of 7-8 mmHg no significant changes were present.(ABSTRACT TRUNCATED AT 250 WORDS)

Models of coronary artery disease: "critical" versus "functional" coronary artery stenosis

"Critical coronary stenosis" (reduction of coronary blood flow [Q] until reactive hyperaemia following 15s coronary occlusion is just abolished) and "functional stenosis" (reduction of Q until systolic shortening (dL) of post-stenotic myocardium is curtailed by 50%) were compared with respect to the reduction in Q necessary and the effect on regional myocardial and global ventricular function. In 9 anaesthetized (piritramide) dogs, enddiastolic length (edL) and dL of a myocardial area supplied by the left descending coronary artery (LAD) were measured by sonomicrometry. Left-ventricular end-diastolic pressure (LVEDP) and dP/dt, aortic pressure (AoP), stroke volume (SV), and heart rate (HR) were monitored. QLAD was stepwise reduced by a snare. Critical stenosis, present at a 25% reduction of QLAD, had no effect on regional and global ventricular function, but recovery of dL after release of 15s LAD occlusion was significantly delayed. Further obstruction of QLAD progressively impaired dL, reaching 50% dL (functional stenosis) by a flow reduction of about 50%. The decrease in dL was accompanied by an increase in edL. The haemodynamic effects of the functional stenosis were rather discrete (LVEDP + 5%, SV-12%, dP/dtmax-8%). Models of myocardial ischaemia used to study the effect of drugs or other haemodynamically effective interventions should be able to show functional impairment as well as improvement of the ischaemic myocardium. The critical stenosis does not impair myocardial function and, consequently, a favourable influence on the function and, consequently, a favourable influence on the function of ischaemic myocardium by any intervention may not become evident. However, in the presence of a functional stenosis the change in systolic shortening of the ischaemic myocardium is a very sensitive response to any intervention which affects the energy balance of the ischaemic myocardium. Therefore, this model should be preferred.

Global and regional ventricular function following intracoronary application of papaverine

Intracoronary injection of papaverine is used to determine coronary flow reserve in patients. The present study was to investigate the effect of papaverine on the performance of myocardium with reduced flow reserve. In nine anaesthetized open-chest dogs a bypass from the aorta to the left circumflex coronary artery (LCX) was established. Left ventricular end-diastolic and aortic pressure, dP/dt, stroke volume, LCX blood flow, and ECG were monitored. The performance of a segment of subendocardial wall supplied by the LCX was assessed by sonomicrometry. Peak reactive hyperaemia after 15s bypass occlusion was 1.44 +/- 0.09 times the baseline flow (41 ml/min), indicating reduced coronary flow reserve. Papaverine was injected into the bypass (0.3, 0.6, 1.2, 2.5, 5.0 mg/ml, 1 ml in 15s). The maximum LCX flow following PAPA 0.3 mg was comparable to peak reactive hyperaemia, but 10-15% higher after injection of 0.6-5.0 mg papaverine. Systolic shortening of the myocardium (control: 17.5% of end-diastolic length) became reduced in a dose-dependent fashion (5-25%) for about 1 min following papaverine injection. Stroke volume (control: 0.94 +/- 0.12 ml/kg) was reduced by about 8%, left ventricular end-diastolic pressure (control: 6.2 +/- 0.8 mmHg) increased by 15%, and dP/dtmin (control: 1850 +/- 150 mmHg/s) was curtailed by 15-25%. The ECG showed a transient T inversion and S-T depression following papaverine administration and in one experiment ventricular fibrillation occurred after the injection of 2.5 mg papaverine. The observed effects of intracoronary papaverine are consistent with the theory of transient subendocardial ischaemia arising from a redistribution of blood flow from the subendocardial to the subepicardial layers, because of greater vasodilatory capacity in the latter than in the former.

Effect of urapidil on the performance of ischemic myocardium in anesthetized dogs

Urapidil (URA) is used to treat acute hypertension in patients with coronary artery disease, but the effect of URA on the performance of ischemic myocardium has not yet been investigated. The present study was intended to assess the function of ischemic myocardium following URA administration. In eight anesthetized (piritramide) open-chest dogs systolic contraction (dL) and end-diastolic length (edL) of myocardium supplied by the left descending (LAD) and circumflex (LCA) coronary arteries were measured by sonomicrometry simultaneously with aortic pressure (AoP), left ventricular end-diastolic pressure (LVedP), heart rate (HR), stroke volume (SV), and LAD-flow (QLAD). QLAD was reduced by LAD stenosis to about 50% of control, decreasing dLLAD by 55%. Concomitantly, edLLAD increased by about 9% and LVedP by 22%, whereas AoP decreased by 5%. Then, URA was given i.v. (0.25 + 0.25 + 0.50 + 1.0 mg/kg) in 15-min intervals. Following URA, the performance of the non-ischemic area was not systematically affected, but dLLAD increased by about 50%. This could neither be related to the significant reduction in afterload (AoP: -8%), nor to an increase in preload (LVedP and edLLAD did not change significantly), nor to an improved oxygen supply via the LAD (QLAD even decreased), although an increased collateral flow the LCA could not be excluded. The increase in systolic shortening correlated very closely to a decrease in heart rate (r = -0.92). It is concluded that the improved function of ischemic myocardium following urapidil resulted from a reduced oxygen demand in consequence to the decrease in heart rate.

Preservation versus severance of the subvalvular apparatus in mitral valve replacement: an experimental study

Preservation of the subvalvular apparatus in mitral valve replacement has been suggested to improve postoperative left ventricular performance. As it is difficult to quantify the change in left ventricular performance clinically, an experimental model was devised to demonstrate the contribution of the subvalvular apparatus to left ventricular function. In eight dogs mitral valve replacement (St. Jude prostheses) was performed, preserving the subvalvular apparatus by plicating the leaflets with the prosthesis on the mitral annulus. Left ventricular function was assessed during volume loading with blood before and after cutting the chordae tendineae by means of electrocautery applied via flexible wires slung around the chordae and exteriorized through the left ventricular wall. Left ventricular internal diameters were measured by sonomicrometry. End-diastolic volume (LVedV) and stroke volume were determined by dye dilution and left ventricular pressure (LVP) by cathter tip manometer. The results showed that after cutting the chordae the heart rate did not differ from the pre-cut values at any LVedP. The peak left ventricular pressure was only significantly reduced at an LVedP of 5 mmHg and minor axis diameters were only increased at an LVedP of 9-12 mmHg. Significant changes were observed, however, in LV dP/dtmax (= maximum rise of LVP) (-15%), major axis end-diastolic diameter (+10%) and systolic shortening (-40%), end-diastolic volume (+18%) and ejection fraction (-16%) at any LVedP, and stroke volume (-24%) at any LVedV.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of urapidil on the performance of ischaemic myocardium in anaesthetized dogs

The effect of urapidil on the ischaemic myocardium was studied in eight anaesthetized dogs. Stenosis of the left descending coronary artery reduced blood flow and systolic contraction of the post-stenotic myocardium by about 50%; the end-diastolic length of the post-stenotic myocardium and the end-diastolic pressure increased, while aortic pressure slightly decreased. Subsequent administration of urapidil (0.25 + 0.25 + 0.5 + 1.0 mg/kg intravenously) did not affect the systolic shortening and end-diastolic length of the myocardium supplied by the left circumflux coronary artery, while the stroke volume and the systolic shortening of the ischaemic myocardium increased. The latter was correlated with a decrease in the heart rate (r = -0.92), but not with the reduction in aortic pressure. Urapidil by itself does not impair the performance of the ischaemic myocardium, but might be beneficial in decreasing the heart rate or suppressing reflex tachycardia during reduction of the afterload.

Effects of pressure-controlled intermittent coronary sinus occlusion on regional ischemic myocardial function

Pressure-controlled intermittent coronary sinus occlusion has been reported to reduce infarct size in dogs with coronary artery occlusion, possibly because of increased ischemic zone perfusion and washout of toxic metabolites. The influence of this intervention on regional myocardial function was investigated in open and closed chest dogs. In six open chest dogs with severe stenosis of the left anterior descending coronary artery and subsequent total occlusion, a 10 minute application of intermittent coronary sinus occlusion increased ischemic myocardial segment shortening from 5.5 +/- 1.2 to 8.2 +/- 2.6% (NS) and from -0.1 +/- 2.1 to 2.3 +/- 1.2% (NS), respectively. In eight closed chest anesthetized dogs, intermittent coronary sinus occlusion was applied for 2.5 hours between 30 minutes and 3 hours of intravascular balloon occlusion of the proximal left anterior descending coronary artery. Standardized two-dimensional echocardiographic measurements of left ventricular function were performed to derive systolic sectional and segmental fractional area changes in five short-axis cross sections of the left ventricle. Fractional area change in all the severely ischemic segments (less than 5% systolic wall thickening) was -4.0 +/- 4.7% at 30 minutes after occlusion, and increased with subsequent 60 and 150 minutes of treatment to 13.1 +/- 3.3 and 7.0 +/- 3.3%, respectively (p less than 0.05). At the most extensively involved low papillary muscle level of the ventricle, regional ischemic fractional area change was increased by intermittent coronary sinus occlusion between 30 and 180 minutes of coronary occlusion from -0.4 +/- 0.1 to 14.4 +/- 4% (p less than 0.05), whereas a further deterioration was noted in untreated dogs with coronary occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

[Isolated aortic isthmus stenosis: operation indications and results]

The goal of surgical correction of isolated coarctation of the aorta is normalization of the blood pressure. To assess the optimal age for the intervention with respect to operative morbidity and mortality, residual stenosis and recoarctation rate as well as the postoperative persistence of arterial hypertension without recoarctation, the pre- and postoperative findings of 237 patients (age at surgery: range one week to 17 years) were analyzed. The blood pressure, which was above the 95th percentile of age-matched normal values preoperatively in 93%, showed a clear decrease postoperatively in all age groups. On surgical correction, however, performed as of six years of age, there was a continuously increasing rate of persistent arterial hypertension without recoarctation which ranged from about 10% in those undergoing surgery between the ages of six and eight years to 31% in patients operated at ages between 13 and 17 years. In consideration of the operative results only with respect to the response of the resting blood pressure, insight is enabled only into one aspect of the prognosis, since the latter is equally dependent on the postoperative systemic arterial resistance. The systemic arterial resistance is already slightly elevated at three to five years of age, significantly increased as of six years of age, and at surgery after the age of six, shows a further increasing tendency. Accordingly, patients with postoperative normal or borderline-elevated blood pressure and apparently adequate surgical results, may be at risk of subsequent development of hypertension due to persistence of increased resistance, in particular, if surgery is performed after the age of five years.(ABSTRACT TRUNCATED AT 250 WORDS)

[Clenbuterol and fenoterol--animal experiment comparison of 2 tocolytic agents (with special reference to cardiovascular side effects)]

During animal experiments two substances, which are used for tocolysis (Fenoterol and Clenbuterol) have been compared regarding their tocolytic efficiency (determinations of myometrial cyclic AMP after long term treatment of the pregnant rat), their effects upon myocardial high energy phosphates (determinations of maternal myocardial high energy phosphates as well as of maternal and fetal myocardial cyclic AMP after long term treatment of the pregnant rat) and upon the hemodynamic situation (acute experiments with thoracotomized dogs). While significant hemodynamic derangements could be stated when using Fenoterol, no significant evidence for such alterations could be found during Clenbuterol administration during acute experiments. Determinations of myocardial high energy phosphates however reflected an augmented myocardial workload, both after Fenoterol and Clenbuterol administration. As by means of myometrial cyclic AMP determinations Clenbuterol proved to be at least as efficient as Fenoterol, concerning the tocolytic effect, Clenbuterol can be recommended as an oral tocolytic because of its pharmaco-cinetic advantages and the encouraging results from our hemodynamic investigations. According to results from chronical experiments an additional cardioprotection by means of magnesium substitution and eventually beta 1-blockade is still recommended.

[The cardiac hazard of tocolysis and antagonizing possibilities. II. Communication: protection of the myocardium by means of substitution of magnesium]

In a comparative study the value of the substitution of magnesium for the evaluation of cardiac side-effects of tocolysis has been assessed with regard to haemodynamic as well as to metabolic and morphologic alterations. Haemodynamic studies at the thoracotomized dog using the technique described in the first publication showed significantly less severe haemodynamic alterations in a group with normal magnesium blood levels than in the second group with reduced magnesium blood levels. Significant differences could be found at systolic blood pressure, cardiac output, velocity and acceleration of pressure rising, total peripherial resistance, myocardial contraction status and myocardial oxygen consumption. Likewise, a beneficial tendency could be found at the parameters: heart rate, Bretschneiders index of inotropy, pulmonal arterial pressure and coronary reserve. During chronic experiments at the rat, the addition of magnesiumaspartate led to a significantly improved preservation of high-energy phosphates in the myocardium with a concomitant reduction of lactic acid output. Also the increase of body weight was significantly higher when substituting magnesium. Microscopic examination showed no irritations of myocardial structure within the magnesium-substituted group, whereas lymphocytic infiltrations and a slight fibrosis of the endocardium could be seen at the animals having received only Fenoterol. Together, these findings lead to the conclusion, that the substitution of magnesium can act prophylactically against cardiac alterations, induced by Fenoterol. Consequently, magnesium deficiency, which frequently accompanies pregnancy, should be balanced before starting a tocolytic therapy.

[The cardiac hazard of tocolysis and antagonising possibilities. I. The haemodynamic situation of the patient during tocolysis/Protection of the myocardium by means of cardioselective beta-blockade. Experimental results (author's transl)]

7 mongrel dogs underwent general anaesthesia and thoracotomy. For the assessment of the haemodynamic situation the following parameters were measured: Left ventricular and aortic pressure, coronary flow, oxygen-saturation in the coronary sinus, pulmonal arterial pressure, central venous pressure, heart rate. From these measurements cardiac output volume and myocardial oxygen consumption could be calculated. Using an ultrasound transit-time method regional myocardial function could be assessed. After the establishment of these measurements Fenoterol has been given in an increasing dosage up to the upper therapeutical range. Then additionally the cardioselective beta-antagonist Metoprolol was administered stepwise up to a total dose of 1.2 mg/kg body weight. The measurements proved evidence, that a relatively small dose of 0,2-0,4 mg Metoprolol/kg body weight is sufficient to compensate the haemodynamic situation impaired by Fenoterol, esp. the rise in myocardial oxygen consumption.

[Hyperoncotic hemodilution in the ewe asa model of therapy in EPH gestosis (author's transl)]

Hyperoncotic hemodilution is proposed as a new therapeutic procedure in EPH-gestosis for improvement of uterine blood flow. By infusion of human albumin solutions in acute experiments on pregnant Merino sheep the effects of altered maternofetal colloid osmotic pressure gradients were investigated. The proposed hemodilution treatment improved uterine blood flow without a theoretically apprehended and undesired fetal hemoconcentration. An absolute indication for hypervolemic EPH-gestosis is suggested in accordance with modern knowledge of the pathophysiology of microcirculation. Isovolemic hemodilution is proposed to be of potential value in cases of EPH-gestosis with normovolemia, hypertension, intrauterine fetal growth retardation or other symptoms of placental insufficiency, at least as a subject to further studies.

Acute effects of aortocoronary bypass surgery on left ventricular function and regional myocardial mechanics: a clinical study

The acute effects of myocardial revascularization on overall left ventricular performance and on myocardial segmental wall motion were assessed intraoperatively in 22 patients who had unstable (11 patients) or stable angina pectoris (11 patients). Segmental contraction patterns were evaluated using an ultrasonic transit-time method. In 9 patients with unstable angina pectoris, notable improvement in segmental wall motion was observed as the short-term response to coronary bypass grafting. Hypokinetic patterns were rendered normal after revascularization. Despite marked changes in segmental myocardial function, overall left ventricular performance was not altered notably. In contrast, reperfusion did not lead to acute effects on either segmental wall motion or total left ventricular function in patients with stable angina pectoris. The results indicate that aortocoronary bypass grafting may improve segmental wall motion in patients with unstable angina.

[External interference of cardiac pacemakers (author's transl)]

The pacemaker patient is faced with potential origins of interference to the pacemaker function in his daily life, at his working place and during medical-therapeutic interventions. Technical faults in the electronic circuit induced by external sources can be neglected. Malfunctions of synchronized cardiac pacemakers may occur in the presence of electrical signals similar to the intracardiac ECG (e.g. nerve stimulators) or by the influence of high energy electrical field (e.g. pulsed electromagnetic fields). Technical improvements like metalshielding of the unit, electronic filtering components and automatic conversion to fixed rate stimulation increase the reliability to a high degree.

[Heart rhythm during esophago-gastro-duodenoscopy]

The ECGs of 157 patients were registered continuously during the oesophago-gastro-duodenoscopy with a R-R intervall monitoring system. The behavior of frequencies and cardiac arrhythms of 53 patients with and 104 patients without heart diseases is reported. 32 patients were premedicated with 0,5 mg Atropin intravenously, 121 patients received intramuscular premedication. The influence of the vegetative nervous system is discussed in view of the heart actions during the diagnostic procedure. A clinically relevant danger for the heart and circulatory system caused by oesophago-gastro-duodenoscopy was not observed.

[Current status of pacemaker technology (author's transl)]

Since the first cardiac pacemaker was implanted twenty years ago, advances rendered have provided patients with increased reliability and therapeutic efficiency as well as subsequent incrementation in their life expectancy. Technological developments have yielded improvement in the main components such as electrode, the energy source and the electronic circuitry. A variety of leads are available to effect pacing requirements at ventricular and, in part, atrial levels. The introduction of lithium energy sources has prolonged the useful life of pacemakers to more than 8 years. Consumption of current has been reduced by decreasing electrode surface area, shortening of pulse duration and employment of hybrid circuits. Microprocessing of the electronic components have enabled reduced size of pulse generators while providing increased reliability and capabilities for additional functions. Amelioration of electrophysiologic disturbances has been specifically approached through increasing use of atrial and bifocal pacemakers, external programmability and overdrive pacing.

[The effect of nitrates on the function of intact and ischemic myocardium (author's transl)]

The effects of Sodium Nitroprusside (NPN), of Isosorbidedinitrate (ISDN), and of a combined therapy with NPN and the intraaortic balloon pump (IABP) on left ventricular function and on local contraction patterns of normal and ischemic myocardial regions were studied. In acute experiments on 16 dogs the anterior descending branch of the left coronary artery was stenosed to produce a hypokinesia or dyskinesia of the anterior wall of the left ventricle. Regional myocardial function was assessed using the ultrasound transit time method. When the LV filling pressure was initially norman (LVedP 5.7 +/- 0.6mmHg) nitrate infusion (120 microgram/minn NPN: 800 microgram/min ISDN) resulted in an aggravation of the ischemic dysfunction. Conversely, with high initial filling pressure (LVedP 15.4 +/- 1.3MMHg) regional myocardial function in the ischemic area returned to normal under therapy. Additional application of the IABP further improved regional myocardial mechanics. It is concluded, that reduction of coronary perfusion pressure due to nitrate therapy becomes critical when coronary reserve is depleted. Compensation is however possible if ventricular wall stress can be reduced and thus the oxygen consumption and the extravascular component of coronary resistance are decreased. Only when the initial filling pressure is high these conditions are met.

The effect of hemodilution on regional myocardial function in the presence of coronary stenosis

Hemodilution decreases blood viscosity and circulatory input impedance and thus reduces afterload. Its use in treatment of LV power failure has been advocated, but the safe limits of isovolemic hemodilution are not known. Compensation of the reduced O2-capacity of the blood was therefore studied with normal and impaired coronary reserve. In 20 dogs the LAD was stenosed to a degree just not affecting the supplied region and central and coronary hemodynamics were studied. Regional myocardial function was assessed by ultrasound transit time between transducers implanted in the LV wall. Lowering the hematocrit to 15% by isovolumic exchange of blood for Dextran 60 increased CVP (18%), PAP (47%), LAP (64%), LVedP (46%), CO (67%), and flow to the intact area (LCA: 211%). Flow in the stenosed LAD increased slightly. Enddiastolic length (EDL) of LAD dependent muscle segments rose to 120% and their contraction amplitude deltaL was decreased by 46%. Whereas non-ischemic segments showed compensatory rise in deltaL (38%) at almost constant EDL (+9%). After release of the LAD stenosis EDL and deltaL returned to normal. During progressive anemia myocardial O2-demand is not adequately met if coronary reserve capacity is depleted. Reversion of hypokinesia after removal of the stenosis shows unimpaired myocardial function at a hematocrit as low as 15% provided the coronary circulation is intact.

[Hemodynamic studies after the implantation of Hancock-heart valves (author's transl)]

Velocity profile, pressure gradient across the valve and blood flow have been measured in 10 patients after the implantation of bioprostheses of the sizes 27 and 29 millimeters in aortic position. According to these hemodynamic measurements the use of bioprostheses for the aortic valve replacement is recommendable. The low flow velocities in the area of the muscle containing valve cusp did not effect a detectable stenosis intraoperatively under the conditions of rest. The hemodynamic data showed no differences between the Hancock-Zuhdi and the Edwards-Carpentier bioprostheses. Despite of good hemodynamic conditions and a low risk of thromboembolic complications after the aortic valve replacement with bioprostheses reservation is recommended to its clinical use until the long term mechanical stability (more than 6 years) of the biological heart valve prosthesis has been secured.

[Direct measurement of papillary muscle dynamics in the intact canine left ventricle during acute coronary occlusion (author's transl)]

The functions of the normal and ischemic papillary muscle in the intact canine heart were studied using an ultrasonic transit time method. Miniaturized piezoelectric crystals (1.5-2 mm 0) were implanted during extracorporeal circulation into the root and tip of the anterior and posterior papillary muscle of the left ventricle.

RESULTS

1. Phasic changes of left ventricular geometry during the heart cycle determine the dynamic pattern of papillary muscle movements. 2. The amplitude and velocity of papillary muscle length is directly related to those of myocardial wall segments. 3. Experimental ischemia induces total dysfunction of the papillary muscle within seconds. 4. Despite total muscle dysfunction no mitral insufficiency occured.

[Instantaneous blood flow velocity profiles before and after aortic valve replacement (author's transl)]

In 17 patients the instantaneous velocity profile was recorded before and after aortic valve replacement (Starr-Edwards, Björk-Shiley, Lillehei-Kaster). A single gated pulsed Doppler Ultrasonic flownmeter was used for analysis. Distal of these valves a flat flow profile was recorded showing high velocity gradients near the walls. As a main cause of this, numerous eddies and turbulent flow have been suggested. Downstream of a Starr valve a flat profile appears with a slowing down of forward flow just behind the ball. The disk valves Lillehei-Kaster and Björk-Shiley demonstrated a higher flow velocity in direction to the larger opening. The "in vivo" studies have been supported by "in vitro" measurements. The highest flow velocities were above 100 cm/sec and thus, according to Reynolds definition, in the turbulent range. The turbulent flow produces a washing effect, which is emphasized during the cardiac cycle. The importance of these data can be discussed by clinical results only.