Hemodynamic effects of oral amiodarone on left ventricular function before and after global ischemia.

We evaluated the hemodynamic effects of amiodarone on left ventricular (LV) function after global ischemia. Amiodarone was administered orally at 15 mg/kg/day for an average of 28 days to a group of 10 dogs. The concentration of amiodarone in serum and LV myocardium was 0.40 +/- 0.24 micrograms/ml and 44 +/- 27.0 micrograms/g, respectively. This experimental group and a control group of 10 dogs each underwent 120 min of aortic cross-clamping with cold crystalloid cardioplegia resulting in an average myocardial temperature of 15 degrees C. LV function measurements by pulse-transit sonomicrometry and Millar solid-state micromanometers were processed by a minicomputer. Compared to the nontreated control group, oral amiodarone for 28 days produced depression of LV contractility which was reflected by lower slope of the end-systolic pressure-volume relation (Evmax), percentage shortening of segment length, left ventricular pressure-segment length loop area, and slope of the end-systolic pressure-segment length relation (Esmax). After ischemia, percentage recovery of LV global function (Evmax and mean velocity of circumferential fiber shortening) and regional function (Esmax) was significantly better in the amiodarone group than in the control group. We conclude that oral amiodarone for 28 days results in a depression of LV contractility but the combination of amiodarone and ischemia does not act synergistically to further depress postischemic LV function.

Diastolic mechanical properties of the left ventricle after global ischemia.

The purpose of this study was to evaluate left ventricular (LV) diastolic mechanical properties after induced global ischemia using reliable new methods. The diastolic function of nonoxygenated crystalloid solution (CC sO2) was compared with those of oxygenated crystalloid (CC cO2) and oxygenated fluorocarbon cardioplegic (FC cO2) solutions. Postischemic ventricular performance was studied in 3 equal (no. 7) groups of dogs subjected to 120 minutes of global ischemia induced at an average myocardial temperature of 18.5 +/- 1.4 degrees C. LV diastolic function (chamber and myocardial stiffness) and relaxation (the exponential fall in LV pressure) were evaluated by sonomicrometry and Millar micrometers before ischemia and at 45 and 60 minutes after ischemia. LV chamber and myocardial stiffness in the CC sO2 group was significantly (p less than 0.05) elevated after ischemia, while the CC cO2 and FC cO2 groups did not show increases in LV chamber and myocardial stiffness after ischemia. LV relaxation before and after ischemia was not changed in any group. The myocardial water content of the CC sO2 group was significantly higher than that of the CC cO2 and FC cO2 groups (p less than 0.05). We conclude that (1) the postischemic increase in LV chamber stiffness in the CC sO2 group was dependent not only on the increase in intrinsic myocardial stiffness but also due to an increase in myocardial edema, and (2) there was no correlation between the LV relaxation rate and the leftward shift of diastolic compliance curves in the CC sO2 group.

Preoperative aspirin therapy and reoperation for bleeding after coronary artery bypass surgery.

We performed a case-control study to estimate the relative risk of reoperation for bleeding in coronary artery bypass graft patients who had taken aspirin within the 7 days preceding surgery. Comparison of 90 cases of reoperation with 180 matched control subjects gave an estimated odds ratio for reoperation of 1.82 (95% confidence interval, 1.23 to 3.32). Although their preoperative coagulation values were similar, cases used significantly more whole blood (cases, 9.5 +/- 5.2 units; control subjects, 3.0 +/- 2.0 units; median +/- interquartile range), packed red blood cells (cases, 2.1 +/- 4.0 units; control subjects, 0.9 +/- 2.0 units), and platelets (cases, 12.2 +/- 12.0 units; control subjects, 2.9 +/- 4.0 units) than control subjects. Cases had intensive care unit stays of 4.7 +/- 5.7 days (mean +/- SD) vs 2.1 +/- 1.9 days for control subjects and postoperative hospitalizations of 10.9 +/- 8.2 days vs 7.0 +/- 3.2 days for control subjects. We conclude that aspirin exposure within 7 days before coronary bypass surgery is associated with an increased rate of reoperation for bleeding and that reoperation is associated with large increases in transfusion requirements and intensive care unit and hospital stays.

Short-term morbidity and mortality of implantation of automatic implantable cardioverter-defibrillator.

Over the 3-year period from Jan. 1, 1986, through Dec. 31, 1988, we have implanted 101 automatic implantable cardioverter-defibrillators into patients with life-threatening ventricular arrhythmias. There were 82 male patients and 19 female patients. The mean age was 58 years with a range of 25 to 82 years. The indication for implantation was ventricular fibrillation in 89 patients and recurrent ventricular tachycardia in 12 patients. Seventy-seven patients had a history of prior myocardial infarction or coronary artery disease, or both. Eighteen patients had nonischemic cardiomyopathy. One patient had a prolonged QT syndrome and five patients had no evidence of preexisting structural heart disease. The mean injection fraction was 37% +/- 17%. Forty-one of the automatic implantable cardioverter-defibrillator implantations were associated with procedures necessitating cardiopulmonary bypass. The hospital mortality rate was 4% and the morbidity rate was 15%. The only statistical difference between those patients who did and did not have postoperative complications was a history of a prior myocardial infarction (90% versus 54%, p less than 0.05). Twenty percent of patients had new-onset postoperative atrial fibrillation after implantation of the device. Eleven percent of patients had sustained ventricular tachycardia postoperatively. Although there was a trend toward a higher complication/death rate in the patients whose automatic implantable cardioverter-defibrillator was inserted in association with cardiopulmonary bypass (24% versus 15%) and the occurrence of new-onset postoperative atrial fibrillation (27% versus 15%), these findings were not statistically significant. Automatic implantable cardioverter-defibrillator implantation with and without concomitant cardiopulmonary bypass is associated with a clinically important morbidity and mortality rate and development of postoperative arrhythmias.

Myocardial preservation: a comparison of oxygenated crystalloid and blood cardioplegia.

The purpose of this experiment was to compare myocardial protective effect after global ischemia using oxygenated crystalloid (CCcO2) and an oxygenated blood (BCcO2) cardioplegic solutions. Post-ischemic ventricular performance was studied in 2 equal (n = 7) groups of dogs subjected to 120 min of global ischemia induced at average myocardial temperatures of 8 degrees C in the CCcO2 group and 18 degrees C in the BCcO2 group. Left ventricular (LV) function included analysis of LV systolic function (global and regional function), LV diastolic function (chamber and myocardial stiffness) and LV relaxation was measured by sonomicrometry and Millar micrometers. Data were processed with a Dec PDP-11/23 computer. In vitro oxygen content (Vol%) measured 3.2 +/- 1.0 (CCcO2) and 9.5 +/- 0.3 (BCcO2). Percent recoveries of LV global function (LVSP, loop area, % shortening, LV dp/dt, mean VCF and E max) in the CCcO2 group were approximately the same as those in the BCcO2 group. There were no significant differences in LV regional function (loop area and % shortening) after ischemia between the two groups. The chamber and myocardial stiffness after ischemia in the CCcO2 group were almost the same as the baseline values. Values in the BCcO2 group were reduced significantly compared to the baseline level. There were significant differences in post-ischemic chamber and myocardial stiffness between the two groups. Post-ischemic maximum negative LV dp/dt in both groups decreased significantly compared to the baseline values. However, the time constant and diastolic interval after ischemia in both groups were approximately the same as the baseline values. We conclude that there were no significant differences in myocardial protective effect between the CCcO2 and BCcO2 groups, and both methods preserved the ischemic myocardium well.

Traumatic rupture of the thoracic aorta in the pediatric patient.

Traumatic rupture of the thoracic aorta is rare in pediatric patients. Proper management of this injury is essential and requires a systematic approach, similar to that used in adult patients. Preoperatively, the multiply injured child must have other injuries properly prioritized and addressed. Proper selection of graft size, expeditious intraoperative management, and careful postoperative management result in a minimal number of complications associated with this injury.

Experimental fluid dynamics of aortic stenosis in a model of the human aorta.

Aortic stenosis has been modelled in an in vitro, pulsatile mock circulatory system (MCS) using a porcine valvular prosthesis, and studied with a laser Doppler anemometer (LDA). The MCS incorporated an acrylic model of the human aorta made from a cadaveric casting in situ. A Carpentier-Edwards aortic valve prosthesis was placed in the MCS after being rendered stenotic by suturing of the valve cusps. Flow velocity profiles across the lumen of the aorta in the presence of aortic stenosis were determined using LDA at two preselected sites in the ascending aorta, and at one preselected site in the brachiocephalic artery. Results indicate that a strong systolic jet bordered by transient vortices with intensely reversed flows is produced distal to severely stenotic aortic valves, becoming less intense with a lesser degree of stenosis. Peak fluid velocities in the systolic jet were determined by LDA at distances of 2.6 and 5.6 cm from the valve inlet for a mean flow rate of 5.2 l min-1. Peak systolic pressure gradients and peak turbulent axial stresses were also determined and found to increase dramatically with stenosis. Furthermore, increasing degrees of stenosis also resulted in more severely disturbed flows in the brachiocephalic artery. Peak fluid velocities and their associated turbulent axial stresses in the systolic jets produced by aortic valvular stenosis are remarkably sensitive to even small changes in the calculated valve orifice areas, and can therefore be very useful in assessing the severity and progression of valvular disease. In addition, increasing degrees of aortic stenosis cause more turbulence to be transported into the brachiocephalic artery.

The use of autologous pericardium for ventricular aneurysm closure.

Closure of the ventriculotomy following ventricular aneurysm resection usually requires buttressing material to provide strength and hemostasis. Although Teflon felt has usually been used, this material is bulky, noncompliant, and prone to infection. Autologous pericardium appears to offer an ideal substitute without the disadvantages of artificial material. A simple technique is described to apply pericardial tissue as a natural buttressing agent for ventriculotomy closure.

Ischemic myocardial protection. Comparison of nonoxygenated crystalloid, oxygenated crystalloid, and oxygenated fluorocarbon cardioplegic solutions.

This study was designed to compare myocardial protection with a nonoxygenated crystalloid solution, an oxygenated crystalloid solution, and an oxygenated fluorocarbon cardioplegic solution. Postischemic ventricular performance was studied in three equal (N = 7) groups of dogs subjected to 120 minutes of global ischemia induced at an average myocardial temperature of 18.5 degrees +/- 1.4 degrees C (range 17.0 degrees to 21.0 degrees C). Left ventricular global and regional function was evaluated by sonomicrometry and micromanometers before ischemia and at 45 and 60 minutes after ischemia. Stroke volume index, left ventricular pressure-minor external diameter loop area, percent shortening, first derivative of left ventricular pressure, mean velocity of circumferential fiber shortening, and the slope of the end-systolic pressure were used to evaluate myocardial contractility. In vitro oxygen content of the three cardioplegic solutions was measured at a mean injection temperature of 8.3 degrees +/- 0.6 degrees C: 0.8 +/- 0.1 vol% (nonoxygenated crystalloid cardioplegia), 3.2 +/- 0.2 vol% (oxygenated crystalloid cardioplegia), and 6.2 +/- 0.2 vol% (oxygenated fluorocarbon cardioplegia). Recovery of global and regional function was significantly (p less than 0.05) better with both oxygenated solutions than with the nonoxygenated solution. Differences between the oxygenated crystalloid and fluorocarbon groups were not significant. We conclude: (1) Compared to nonoxygenated crystalloid cardioplegia, oxygenated crystalloid and oxygenated fluorocarbon cardioplegic solutions gave superior myocardial protection during 2 hours of ischemic arrest; (2) no difference was found in protective effects between an oxygenated crystalloid and an oxygenated fluorocarbon solution.

Regional myocardial protection by retrograde coronary sinus infusion of cardioplegic solution.

Antegrade administration of a cardioplegic solution in the presence of a coronary artery stenosis may lead to the heterogeneous distribution of the agent and poor myocardial cooling distal to a vessel stenosis. To determine the effects of retrograde coronary sinus infusion of cardioplegic solution, coronary stenosis was created in the canine preparation by occluding the left circumflex artery (LCx) during cardioplegic arrest. Left ventricular global and regional function (assessed by sonomicrometry and solid-state micrometers) were studied after 60 min of ischemic arrest. Three groups (all n = 7) were studied: group I (control), cardioplegic solution infused via the aortic root without LCx occlusion; group II, same as group I except with LCx occlusion; group III, retrograde coronary sinus infusion of cardioplegic solution with LCx occlusion. Heart rate was controlled by atrial pacing. Statistically significant differences in global function between the three groups were seen at low filling pressures but were not seen during volume challenge. However, the recovery ratio of regional function in the LCx area at a left atrial pressure of 5 mm Hg in group II was 77.2% (% shortening) and 48.5% (segment work), which was significantly less (p less than .01) than recovery in group I (111.7% and 75.9%) and group III (108.3% and 81.5%). These differences persisted during volume loading, to a mean left atrial pressure of 15 mm Hg. Regional compliance in group II was also significantly (p less than .01) depressed after cardioplegic arrest but was well preserved in groups I and III.(ABSTRACT TRUNCATED AT 250 WORDS)

Patch closure of aortic annulus mycotic aneurysms.

Twenty-three patients with bacterial endocarditis and mycotic aneurysms of the aortic annulus were treated between 1978 and 1985. There were 18 men and 5 women ranging from 24 to 72 years old. All patients had congestive heart failure and positive blood cultures as a complication of the endocarditis and were in New York Heart Association (NYHA) Functional Class III or IV. The aneurysm complicated late prosthetic valve endocarditis in 7 patients and native valve endocarditis in 16. The most common infecting organisms were streptococci (12 patients) and staphylococci (7 patients). The noncoronary sinus was the most frequent site for aneurysm formation. Following debridement of the abscess cavity, the orifice of the aneurysm was closed with a patch of Dacron in 20 patients and autologous pericardium in 3. A prosthetic valve (18 bioprosthetic and 5 mechanical) was secured to the noninfected portion of the native annulus and to the patch at the level of annulus. There were 3 deaths, 1 perioperative and 2 late, each without evidence of residual infection or aortic insufficiency. There are 20 late survivors (87%). After a mean follow-up of 1 year, all patients are in NYHA Functional Class I. Patch closure of mycotic aneurysms involving the aortic annulus permits aggressive debridement of the abscess cavity and affords closure of the orifice without tension. The prosthetic valve can be seated at the level of the native annulus, thus avoiding complicated reconstructive procedures of the aortic root and coronary arteries. This technique is an effective alternative in selected cases of mycotic aneurysms involving the aortic annulus.

Oral verapamil for prophylaxis of supraventricular tachycardia after myocardial revascularization. A randomized trial.

To determine if the prophylactic administration of oral verapamil is effective in reducing the incidence of supraventricular tachycardia after myocardial revascularization, 141 patients were entered into a double-blind randomized trial. Seventy patients received verapamil 80 mg every 8 hours beginning immediately after operation and continuing for 5 days, and 71 patients received placebo. Patients were monitored during the study period and observed for the occurrence of supraventricular tachycardia. The verapamil and placebo groups were similar with regard to sex, age, preoperative antianginal drugs, number of bypass grafts, average bypass time, and average occlusion time. A total of 39 patients had supraventricular tachycardia, 20 were receiving verapamil, and 19 were receiving placebo. The average ventricular rate was 127 +/- 13 beats/min for the verapamil group with supraventricular tachycardia compared with 140 +/- 12 beats/min for the placebo group with the mean differences not significant (p = 0.10). On the basis of these data, it is concluded that verapamil 80 mg every 8 hours beginning early after myocardial revascularization is not effective in reducing the incidence of supraventricular tachycardia.

Hypoperfusion as a possible factor in the development of gastrointestinal complications after cardiac surgery.

This study has presented the spectrum of postoperative gastrointestinal system complications after open heart surgery at the University of Washington from 1980 through 1983. The frequent necessity for operative intervention and a mortality rate of 17 percent in our study of gastrointestinal complications in patients who have undergone open heart surgery indicates the need for early diagnosis and treatment. The data suggest that bypass times approaching 100 minutes and the presence of postoperative cardiogenic shock are important risk factors in the development of such complications in elective cardiac surgery patients. An incidence of gastrointestinal complications of 8.6 percent in those undergoing repair of acute aortic dissections makes gastrointestinal complaints particularly suspicious in this subgroup.

Surgical management of refractory ventricular arrhythmias in patients with prior inferior myocardial infarction. A preliminary report.

Most reports of operations for ventricular arrhythmia have dealt with patients with anterior myocardial infarction. Patients with previous remote inferior myocardial infarction and recurrent ventricular tachycardia or fibrillation are a difficult subset of patients to treat with surgical ablative procedures. Over a 2 year period, 11 patients with prior inferior myocardial infarction and drug-refractory ventricular tachycardia or fibrillation underwent elective operation to control the arrhythmia. Five patients had monomorphic ventricular tachycardia. Three of these five patients had localized endocardial resection and/or cryoablative procedures when the ventricular tachycardia was well localized intraoperatively. In the remaining two patients, ventricular tachycardia was noninducible intraoperatively, and the patients underwent extensive endocardial resection and mitral valve replacement because of sites suspected near the posterior papillary muscle from preoperative catheter mapping. None of these five patients had inducible ventricular tachycardia postoperatively, and all are clinically free of the arrhythmia over a 24 month follow-up period. One patient with two morphologies of ventricular tachycardia previously had an unsuccessful blind endocardial resection. She underwent map-directed cryoablation of both sites of ventricular tachycardia. Postoperatively, the patient was free of inducible arrhythmia and has been asymptomatic over 8 months. Five patients had pleomorphic ventricular tachycardia or fibrillation that could not be electrically localized. One patient with ventricular fibrillation underwent extensive endocardial resection, but the posterior papillary muscle was spared. Postoperative electrophysiological study was positive. The patient has had no clinical ventricular arrhythmias on a regimen of amiodarone, however. Two patients had extensive endocardial resection and mitral valve replacement. One died early in the postoperative course and the other is clinically well. The remaining two patients had an encircling endocardial ventriculotomy. Both are clinically stable although one had inducible ventricular fibrillation postoperatively. We conclude that well-defined monomorphic ventricular tachycardia in patients with a previous inferior myocardial infarction can be successfully treated with localized endocardial resection and/or cryoablation. However, patients with poorly localized monomorphic ventricular tachycardia or pleomorphic ventricular tachycardia or fibrillation may require more extensive procedures. The role of posterior papillary muscle sacrifice with mitral valve replacement remains undefined.(ABSTRACT TRUNCATED AT 400 WORDS)

Management of patients with carotid bruit undergoing cardiopulmonary bypass.

During a 31 month period, 1,433 consecutive patients undergoing cardiac procedures were screened for carotid bruit. A total of 94 patients with carotid bruit were identified who had ultrasonic carotid duplex scans. Nine patients had a history of transient ischemic attack, carotid bruit, and reduction in internal carotid artery diameter by greater than or equal to 50% according to ultrasonic carotid duplex scanning. All nine patients underwent carotid angiography followed by thromboendarterectomy prior to or simultaneous with cardiopulmonary bypass. There was one neurological complication leading to death in this subset. Sixteen patients with asymptomatic carotid bruit had ultrasonic carotid duplex scanning revealing an internal carotid artery lesion of greater than or equal to 50% but did not undergo arteriography or thromboendarterectomy prior to the cardiac procedure. Perfusion pressure was maintained at greater than or equal to 70 mm Hg during bypass. There were no focal neurological events in this subset. Sixty-six patients with internal carotid artery stenosis of less than 50% diameter reduction and asymptomatic bruits had no further work-up or modification in perfusion technique, and there were no focal neurological events in this group. Thus there were no focal neurological events in any of the 82 patients with asymptomatic carotid bruit. An additional group of three patients with a previous stroke and internal carotid artery occlusion by ultrasonic carotid duplex scanning had transient exacerbation of neurological symptoms after cardiopulmonary bypass. The remaining 1,339 patients without carotid bruit had nine (0.7%) focal neurological events postoperatively. We believe that asymptomatic patients with or without hemodynamically significant stenosis can safely undergo cardiopulmonary bypass procedures without carotid thromboendarterectomy. Patients with asymptomatic bruits can be safely screened with ultrasonic carotid duplex scanning and do not require arteriography prior to cardiopulmonary bypass.

Pulmonary valve replacement for regurgitation after repair of tetralogy of Fallot.

In general, it has been thought that pulmonary valve insufficiency is well tolerated when the valve is excised or when the pulmonary annulus has been widened with an outflow patch during repair of tetralogy of Fallot. However, when pulmonary regurgitation is massive or when it is combined with other causes of right ventricular failure, progressive right ventricular dilation may occur in some patients. Pulmonary valve replacement has not been commonly used in the past. From January, 1980, to August, 1982, 12 patients, 11 months to 17 years old, had pulmonary regurgitation treated by insertion of a valve in the pulmonary position 4 1/2 months to 11 years after initial repair of tetralogy of Fallot. All patients had progressive right ventricular failure not responsive to medical management. There were no major outflow tract obstructions, residual ventricular septal defects, or persistent aortopulmonary shunts. All 12 patients underwent patch reconstruction of the right ventricular outflow tract that allowed placement of a larger valve. There have been no operative or late deaths, and each patient has had improvement in functional status. One patient required tricuspid valve replacement 1 1/2 years after pulmonary valve replacement to achieve sustained relief of symptoms. Only 1 other patient required subsequent operation; this was for pacemaker lead changes. These early results suggest that in patients with right ventricular failure, attention should be directed to pulmonary regurgitation since this is a component of failure that is reversible; pulmonary valve replacement carries a low risk, and it can relieve symptoms and prevent further deterioration of right ventricular function.

The functional implications of scintigraphic measures of myocardial ischemia and infarction.

To compare serial functional and perfusion scintigraphic changes after myocardial infarction, we performed left ventricular (LV) cineangiograms and thallium (TI)-201 myocardial perfusion scintigrams before and 1 hour, 2 days, 9 days, and 1 month after closed chest coronary occlusion in 14 dogs as survival permitted. Survivors were studied with technetium-99m (stannous) pyrophosphate (TcPYP) scintigrams at 48 hours, and at postmortem examination infarction was documented and measured after nitroblue tetrazolium (NBT) staining. The TcPYP image was abnormal in 10 dogs, each of which had infarcts on NBT staining measuring 3 to 23 gm. In all 14 dogs, perfusion scintigrams became abnormal and LV ejection fraction (EF) fell when measured within 48 hours of occlusion. In the nine late survivors studied over 1 week after the event, perfusion scintigrams and EF improved in those which developed infarcts and normalized in those without infarction. The decrement in LVEF after coronary occlusion generally showed serial improvement and correlated with the size of the defect in the accompanying TI-201 scintigram (r = 0.74). TI-201 defect size seen in late studies correlated well with NBT infarct size (r = 0.89) and TcPYP image infarct size (r = 0.82), as it did with the decrement in LVEF noted in late studies (r = 0.86). The results suggest that early perfusion scintigrams together with TcPYP images may be useful for estimating the amount of reversible dysfunction after coronary occlusion.

Left ventricular outflow enlargement by the Konno procedure.

The optimal management of patients with small aortic anulus or left ventricular outflow tract obstruction remains unclear. Between 1976 and March, 1982; 18 patients have undergone enlargement of their left ventricular outflow tract by means of the Konno or a modification of the Konno procedure. Fourteen of these 18 patients had previous operations for aortic stenosis or tunnel left ventricular outflow tract, and two patients had undergone three previous operations. All 18 patients had symptoms of either heart failure of chest pain, or had electrocardiographic evidence of strain. They ranged in age from 4 years to 58 years, with 13 of the 18 patients being less than 20 years of age. A Dacron patch was used to enlarge the left ventricular outflow tract after incising down the ventricular septum. In all patients, at least a 21 mm valve could be placed, with between 50% and 65% of the valve anulus being made up of natural tissue. The remaining portion of the valve anulus was constructed from the Dacron patch. The patch was extended up to enlarge the ascending aorta, and a pericardial patch was used to close the defect in the right ventricular outflow tract. In all 18 patients the gradient was obliterated at the time of operation. There was one early death in a patient who had previous insertion of a left ventricular apical-aortic conduit in which the heterograft valve had degenerated. There has been one late death because of bacterial endocarditis in a child who also had a parachute mitral valve and evidence of pulmonary hypertension. The remaining 16 patients are functioning well after the Konno procedure. Three are receiving warfarin sodium, and 13 are receiving aspirin. These results suggest that this is an acceptable method of treating patients with small aortic anulus or left ventricular outflow tract obstructions and would appear to have advantages over a left ventricular apical-aortic conduit.

Effect of the normal pericardium on the left ventricular diastolic pressure-volume relationship.

Closed chest placement of tantalum screws in the endocardium was performed an biplane cineradiography of these markers was used to measure LV dimensions while changing total blood volume. Measurements were then repeated following thoracotomy, pericardiotomy and reclosure of the thorax. The LV pressure-volume curves obtained after pericardiotomy always were shifted down and to the right from curves obtained before thoractomy and pericardiotomy. The divergence between the curves increased as LV volume increased, the curves being identical at small LV volumes and at low diastolic pressures. In each experiment the curves diverged before LV diastolic pressure exceeded 10 mm Hg, however.