Stentless aortic valve replacement with Freestyle or Toronto SPV: an early comparison.

BACKGROUND: Stentless aortic xenograft valves have been developed to overcome the disadvantages of conventional stented prostheses. We have implanted two new aortic bioprostheses: the Medtronic Freestyle and the St. Jude Toronto SPV. Early results are compared. METHODS: Forty-four Freestyle valves were implanted using a freestanding total root technique. Fourteen subcoronary Toronto SPV bioprostheses were implanted. Sixty-four percent of both groups (28 of 44 Freestyle and 9 of 14 Toronto SPV) underwent concurrent procedures. RESULTS: Ischemic time was 117 +/- 21 minutes for Freestyle and 124 +/- 19 minutes for Toronto SPV. There were no operative deaths or valve-related reoperations. Aortic valve area was 1.83 +/- 0.51 cm2 for Freestyle and 1.80 +/- 0.51 cm2 (p = 0.89) for Toronto SPV. Transvalvular gradient was 8.03 +/- 4.09 mm Hg for Freestyle and 12.4 +/- 1.82 mm Hg (p = 0.002) for the Toronto SPV. Aortic regurgitation was not experienced in any Freestyle patients, while Toronto SPV patients were graded as none to trace 79% (11 of 14), mild 14% (2 of 14), and moderate 7% (1 of 14). CONCLUSIONS: Aortic valve replacement with the Freestyle and Toronto SPV required equal time for implantation and had equal effective orifice areas. Freestyle had lower transvalvular gradient and less aortic insufficiency without increasing morbidity or mortality.

Aortic root replacement with the freestyle stentless porcine aortic root bioprosthesis.

BACKGROUND: Stentless porcine prosthetic valves offer several advantages over traditional valves. Among these are superior hemodynamics, laminar flow patterns, lack of need for anticoagulation and perhaps improved durability. METHODS: One hundred and twelve patients were operated on from September 17, 1992 to April 13, 1998 as part of a multi-center worldwide investigation. All patients received a total aortic root replacement. Patients were evaluated postoperatively at discharge, 3 to 6 months, and yearly by clinical exam and color flow Doppler echocardiography. RESULTS: There were 4 deaths either in the hospital or within 30 days after surgery for an operative mortality of 3.6%. No patients experienced structural valve deterioration, non-structural valve deterioration, paravalvular leak, unacceptable hemodynamic performance, or postoperative endocarditis. The linearized rates for survival and thromboembolic complications at 5 years were 82.8% and 90.5% respectively. Excellent hemodynamic function is demonstrated by very low gradients, large EOA, and an exceedingly low incidence of any aortic regurgitation. CONCLUSIONS: The Medtronic Freestyle aortic root bioprosthesis can be used safely to replace the aortic root for aortic valve and aortic root pathology. Root replacement allows optimal hemodynamic performance with no significant aortic regurgitation. Early and intermediate results are encouraging, but further follow-up is needed to determine valve durability.

Comparison of results using "freestyle" stentless porcine aortic root bioprosthesis with cryopreserved aortic allograft.

Aortic valve replacement with natural heart valves offer the advantages of superior hemodynamics, laminar flow patterns, lack of need for anticoagulation, and perhaps improved durability. This study compares 5-year results for two stentless aortic valves. In 1992, two prospective clinical trials using two different stentless aortic valves were initiated at our center. The Freestyle stentless porcine aortic root bioprosthesis (SPB) was placed in 106 patients, and cryopreserved aortic allografts (CAA) were placed in 174 patients using a freestanding total root replacement technique in each series. The mean systolic gradient for the SPB was 7.5+/-4.4 mm Hg at discharge and 5.9+/-3.1 mm Hg at 5 years. The mean systolic gradient for the CAA was 6.4+/-3.3 mm Hg at discharge and 5.0+/-2.2 mm Hg at 5 years. At discharge 92.2% of SPB patients had no aortic insufficiency (AI) and 7.8% had trivial AI. In all, 92.9% of CAA patients had no AI at discharge, and 7.1% had mild AI. At 5-year follow-up, 100% of the SPB had no AI, and only 20% of the allograft patients had no AI. The remainder, 80%, had mild AI. Excellent hemodynamic function was seen with both SPB and CAA. A lower incidence of nonhemodynamically significant AI was observed in the SPB group. Preoperative factors such as chronic renal failure and endocarditis may have adversely affected durability in the allograft group, but long-term follow-up is still required to determine durability.

Risk factors and solutions for the development of neurobehavioral changes after coronary artery bypass grafting.

BACKGROUND: As operative mortality for coronary artery bypass grafting has decreased, greater attention has focused on neurobehavioral complications of coronary artery bypass grafting and cardiopulmonary bypass. METHODS: To assess risk factors and to evaluate changes in surgical technique, between 1991 and 1994 we evaluated 395 patients undergoing coronary artery bypass grafting with an 11-part neurobehavioral battery administered preoperatively and at 1 and 6 weeks postoperatively. Patients were instrumented with 5-MHz focused continuous-wave carotid Doppler transducers intraoperatively to estimate cerebral microembolism as an instantaneous perturbation of the velocity signal. Microembolism data were quantitated and compared with surgical technical maneuvers during operation and with neurobehavioral deficit (> or = 20% decline from preoperative performance on two or more neurobehavioral tests) postoperatively. These data and patient demographics were statistically analyzed (chi2, t test) and the results at 2 years (1991 and 1992; group A) were used to influence surgical technique in 1993 and 1994 (group B). RESULTS: Significantly associated with new neurobehavioral deficits were increasing patient age (p < 0.05), more than 100 emboli per case (p < 0.04), and palpable aortic plaque (p < 0.02). Group B patients had a significant decline in the neurobehavioral event rate (group A, 69%, 140/203; versus group B, 60%, 115/192; p < 0.05) of postoperative neurobehavioral deficits at 1 week and at 1 month (group A, 29%, 52/180; versus group B, 18%, 35/198; p < 0.01). The stroke rate was less than 2% in both groups (p = not significant). Modifications of surgical technique used in group B patients included increased use of single cross-clamp technique, increased venting of the left ventricle, and application of transesophageal and epiaortic ultrasound scanning to locate and avoid trauma to aortic atherosclerotic plaques. CONCLUSIONS: Neurobehavioral changes after coronary artery bypass grafting are common and associated with cerebral microembolization. Surgical technical maneuvers designed to reduce emboli production may improve neurobehavioral outcome.

Accuracy of transesophageal echocardiography in preoperative determination of aortic anulus size during valve replacement.

This prospective, blinded study evaluated the accuracy of transesophageal (TEE) and transthoracic echocardiography in predicting the size of the surgical aortic valve anulus in 20 consecutive patients undergoing aortic valve replacement. TEE was highly accurate in predicting surgical aortic valve anulus size (r = 0.98; p < 0.00001). The standard error of the TEE estimate of the size of the obturator anulus was only 0.04 mm, and in all cases the TEE estimate was within 1 mm of the direct surgical measurement. Both biplane and multiplane TEE probes were equally accurate and this accuracy was maintained over a wide range of sizes of surgical aortic anulus. Transthoracic echocardiography appeared less accurate in predicting anulus size (r = 0.64; p < 0.08). Therefore TEE can be used routinely for selection and preparation of aortic allografts before sternotomy, potentially reducing cardiopulmonary bypass pump time by 10 to 30 minutes and ensuring optimal size matching of the donor-recipient anulus.

Acute right ventricular failure during aortic valvular operation due to mechanical problem in the right coronary artery.

BACKGROUND: When right ventricular failure occurs during aortic valvular operation, inadequate myocardial protection may be the culprit. However, other causes of right ventricular failure should be considered, such as air or particulate matter embolization. Right ventricular failure unexpectedly occurred during an aortic valvular operation, and the cause was found to be a mechanical problem with the right coronary ostium. METHODS: A mechanical problem with the right coronary artery (RCA) occurred in 9 patients undergoing aortic valvular procedures, which included isolated aortic valve replacement (4 patients), aortic valve replacement and coronary artery bypass (1 patient), Bentall procedure (2 patients), aortic valve reconstruction (1 patient), and double valve replacement and coronary artery bypass (1 patient). Although myocardial protection was considered to be the cause, a mechanical problem was subsequently identified in the RCA, leading that artery to be bypassed with a segment of saphenous vein. RESULTS: The 1 patient in whom the condition was not recognized at time of aortic valve operation died; at autopsy, a damaged and occluded right ostium was confirmed. The other 8 patients who had the RCA bypassed survived. CONCLUSIONS: We conclude that when right ventricular failure unexpectedly occurs during an aortic valvular operation and does not improve with reperfusion, a mechanical problem in the RCA should be considered. In this situation we recommend that the RCA be bypassed with a segment of saphenous vein graft.

Milestones in the development of cardioplegia.

Long before there was a possibility for the application of cardioplegia to clinical situations, physiologists and surgeons studied the influence of various cations on function of the myocardial cell. These monumental studies helped set the stage for the eventual practical application of various means of myocardial preservation once open cardiac surgical techniques became available. This presentation attempts to summarize early research effort from the work of Sidney Ringer in 1878 until the present time. The historical progression of myocardial protective strategies is reviewed in a sequential fashion, highlighting major contributions and practices of investigators at the time. It is hoped that such a review of the accomplishments of our colleagues past and present will improve our perspective regarding current applications of such knowledge and that it may stimulate further inquiry toward improving present-day myocardial preservation strategies.

Comparison of implantation techniques using freestyle stentless porcine aortic valve.

Stentless porcine aortic valves demonstrate superior hemodynamic performance when compared with their stented counterparts. The technical considerations for implanting these valves can be demanding. The Medtronic Freestyle aortic root bioprosthesis resembles an allograft, has zero-pressure-fixed leaflets treated with an antimineralization agent, and can be implanted using a variety of techniques. In this study of that valve, total root replacement (TRR) was compared with a partial scallop aortic inclusion technique (PSI). Implications were performed in 75 patients (49 PSI and 26 TRR). There were no significant differences with respect to age, sex, or incidence of concomitant procedures. Mean aortic cross-clamp times were significantly less in the PSI group than in the TRR group (51.8 +/- 11.7 minutes versus 125.5 +/- 19.7 minutes; p = 0.0001). At discharge, mean systolic gradients seen on color-flow Doppler echocardiography were less in the TRR group than in the PSI group (6.17 +/- 3.66 versus 10.01 +/- 4.83 mm Hg; p = 0.014). Discharge echocardiography revealed trivial valve regurgitation in 8.3% of the TRR group and in 41.7% of the PSI group (p = 0.004). No patient experienced any significant valvular regurgitation on discharge echocardiography. We conclude that early experience with the Medtronic Freestyle aortic root bioprosthesis shows excellent short-term function regardless of implantation technique. Shorter cross-clamp times, comparable with those of stented valve procedures, occurred with PSI implantation. We anticipate that effects on long-term durability will be beneficial.

Effect of cardiopulmonary bypass on hand and forearm blood flow.

We have assessed the relationship between the aorto-radial pressure difference at the conclusion of cardiopulmonary bypass and blood flow to the hand. Hand blood flow was estimated from the difference between forearm blood flow measured without and with exclusion of the hand circulation. On the same hand, the skin temperature on the palm and on the middle finger was recorded, with the amplitude of the finger pulse oximeter trace. The aorto-radial pressure difference, after cardiopulmonary bypass, correlated with hand blood flow (r = 0.59, P = 0.002). There was a significant (P < 0.0001) palm-finger temperature gradient before and after cardiopulmonary bypass. In conclusion, while the mean aorto-radial pressure difference after bypass results from increased hand blood flow, the finger is not a reliable site to assess the state of the systemic circulation, before or after cardiopulmonary bypass.

Predictive value of blood clotting tests in cardiac surgical patients.

This study prospectively evaluated numerous tests of clotting function in 897 consecutive adult cardiac surgical patients over 18 months. This included coronary operation, valve replacement, and reoperative patients. The tests included activated clotting time, activated partial thromboplastin time, prothrombin time, thrombin time, fibrinogen, fibrin/fibrinogen degradation products, platelet count, and Duke's earlobe bleeding time. Other variables such as age, sex, and cardiopulmonary bypass duration were included in the multivariate analysis. Statistically significant correlations were found between 16-hour mediastinal drainage and activated partial thromboplastin time, fibrinogen, activated clotting time, fibrin/fibrinogen degradation products, platelet count, and prothrombin time. Scatter plots indicate that these relationships, although statistically significant, had little predictive value and were largely significant as a result of the large number of patients in each group, which permitted weak correlations to reach statistical significance. The best multivariate model constructed could explain only 12% of the observed variation in postoperative blood loss. Because the predictive values of the tests are so low, it does not appear sensible to screen patients routinely using these clotting tests shortly after cardiopulmonary bypass.

Combined inotropic effects of amrinone and epinephrine after cardiopulmonary bypass in humans.

Amrinone, a phosphodiesterase inhibitor, and epinephrine, an alpha- and beta-adrenergic receptor agonist, are inotropic drugs used during cardiac surgery to reverse myocardial depression after cardiopulmonary bypass. However, these drugs have not been compared separately, or in combination, in this patient population. We hypothesized that the combination might have complementary actions in improving myocardial function. We, therefore, compared amrinone, epinephrine, and the combination of amrinone and epinephrine in a randomized, blinded, placebo-controlled study in patients undergoing coronary artery bypass grafting. Forty patients with ejection fractions > 0.45 were studied. Right ventricular ejection fraction pulmonary artery catheters and radial arterial catheters were inserted before fentanyl-midazolam anesthesia. After separation from bypass, patients received either a placebo (n = 20) or amrinone bolus (1.5 mg/kg, n = 20) at time 0 and a placebo (n = 20) or epinephrine (30 ng.kg-1.min-1, n = 20) infusion at time 5 min. This resulted in four study groups, n = 10 in each group. Data were collected every 2.5 min for 10 min. Epinephrine, amrinone, and the combination of both drugs significantly increased cardiac output, stroke volume, O2 delivery, and left ventricular stroke work. The increase in stroke volume (P < 0.05) was 12 +/- 6, 16 +/- 4, and 30 +/- 4 mL/beat with epinephrine, amrinone, and the combination of amrinone and epinephrine, respectively. The amrinone-epinephrine combination increased stroke volume as much as the sum of amrinone and epinephrine given separately. Systemic vascular resistance and pulmonary vascular resistance decreased with amrinone and amrinone-epinephrine, but not with epinephrine. Epinephrine increased mean arterial and mean pulmonary arterial pressures. Right ventricular ejection fraction did not significantly increase (P = 0.09) with epinephrine, but increased significantly with amrinone (0.45 to 0.53, P = 0.01), and with the combination (0.43 to 0.55, P = 0.006). These data indicate that amrinone and epinephrine effectively increase myocardial performance during cardiac surgery. Right ventricular function especially was improved with amrinone and the combination of amrinone and epinephrine. The combined effects of amrinone and epinephrine may be useful in patients recovering from the ischemia and reperfusion injury resulting from coronary artery bypass grafting.

Mitral valve operation via an extended transseptal approach.

The extended transseptal approach to the mitral valve has been used for 71 consecutive procedures. Four patients died; none had complications directly attributable to the exposure. Twenty underwent a primary reparative procedure; 30, a primary replacement procedure; and 21, a repeat procedure. Despite division of the sinus node artery, 26 of 32 patients with sinus rhythm preoperatively had sinus rhythm postoperatively; 4 had atrial fibrillation postoperatively. Twenty-seven of 37 patients with atrial fibrillation preoperatively had atrial fibrillation postoperatively; 8 had sinus rhythm postoperatively. Because the exposure provided by this extended transseptal approach is superior to that of standard approaches, we now use it routinely for mitral valve operations.

Magnetic resonance imaging evaluation of recipient for cryopreserved aortic allograft.

Aortic valve replacement with a cryopreserved aortic allograft is the procedure of choice for many patients with aortic valvular heart disease. We have used magnetic resonance imaging preoperatively to determine annular size and coronary artery orientation in the recipient, which not only has enabled us to select an allograft of appropriate size from a distant tissue bank, but also has helped us to identify preoperatively the recipient with a truly bicuspid valve in which the coronary arteries are oriented 180 degrees apart. Sixteen consecutive patients were evaluated preoperatively, the aortic annulus being measured with both magnetic resonance imaging and echocardiography. Cryopreserved aortic allografts were ordered on the basis of the magnetic resonance imaging measurement. Annular size was then measured intraoperatively with calibrated sizers. Magnetic resonance imaging annular measurements correlated highly with those found at operation (r = 0.92), whereas echocardiographic measurements correlated less well (r = 0.69). Coronary orientation was accurately predicted in every case (r = 1.0). Therefore, we have found magnetic resonance imaging to be useful in the preoperative evaluation of patients for aortic valve replacement with a cryopreserved aortic allograft.

Perforation of the anterior mitral leaflet caused by aortic valve endocarditis: diagnosis by two-dimensional, transesophageal echocardiography and color flow Doppler.

Perforation of the mitral valve as a result of aortic valve endocarditis is rare. Recognition of such abnormality is very important before surgical intervention. Diagnosis is very difficult by either invasive or noninvasive techniques. This report stresses the role of echocardiography in evaluating this rare abnormality. Perforation of the anterior mitral valve leaflet developed in our patient as a complication of aortic valve endocarditis. The perforation was suggested by the surface echocardiogram (as an interruption of the leaflet continuity) and by the color flow Doppler (which suggested turbulent flow at the area of suspected interruption). The perforation was confirmed during surgery by transesophageal echocardiography and alerted the surgeon to repair, rather than replace, the valve.

Heparin management protocol for cardiopulmonary bypass influences postoperative heparin rebound but not bleeding.

A group of 63 adult patients undergoing cardiac surgical procedures requiring cardiopulmonary bypass (CPB) were studied to examine the relationship between heparin doses administered and postoperative bleeding. Patients were randomly assigned either to receive heparin 200 U/kg and additional heparin as needed to reach and maintain an activated clotting time (ACT) greater than 400 s for CPB (group A, n = 30), or to receive heparin 400 U/kg and additional heparin as needed to reach and maintain a whole blood heparin concentration greater than 4.0 U/ml for CPB (group H, n = 33). Groups were compared for the amount of postoperative bleeding, heparin rebound, homologous transfusion requirements, and standard laboratory coagulation tests. In the last 33 patients studied, additional tests of platelet aggregation and plasma levels of beta thromboglobulin (BTG), antithrombin III, and several markers of fibrinolysis were measured and compared by group. The mean heparin dose was 28,000 +/- 4,800 U for group A and 57,000 +/- 10,700 U for group H (P less than 0.05 for group A vs. group H). At 8 and 24 h postoperatively, mediastinal drainage did not differ significantly between groups (mean 24-h drainage +/- SD = 901 +/- 414 ml in group A, 1035 +/- 501 ml in group H), nor did the incidence of transfusion with homologous blood products.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebrovascular and cerebral metabolic effects of alterations in perfusion flow rate during hypothermic cardiopulmonary bypass in man.

Recent experimental and clinical investigations provide conflicting evidence regarding the effects of changes in the systemic flow rate from the pump oxygenator on cerebral blood flow and the cerebral metabolic rate of oxygen consumption. However, the results of existing clinical studies are difficult to interpret because of the confounding effects of differences in management of arterial carbon dioxide tension and use of anesthetic and vasoactive agents during cardiopulmonary bypass. To clarify the relationship among perfusion flow rate, cerebral blood flow, and cerebral metabolic rate of oxygen consumption in man during hypothermic cardiopulmonary bypass, we varied perfusion flow rate in random order to either 1.75 or 2.25 L.min-1.m-2 and studied cerebral blood flow (measured by clearance of xenon 133) and cerebral metabolic rate of oxygen consumption (estimated as the product of cerebral blood flow and the cerebral arteriovenous oxygen content difference) in patients managed with both the alpha-stat (group 1) and the pH-stat (group 2) methods of pH and arterial carbon dioxide tension adjustment. We measured the cerebral arteriovenous oxygen content difference using radial arterial and jugular venous bulb blood samples. In each patient other variables known to exert effects on cerebral blood flow and cerebral metabolic rate of oxygen consumption, including temperature, arterial carbon dioxide tension, arterial oxygen tension, mean arterial pressure, and hematocrit, were maintained constant between measurements. In both groups, mean arterial pressure at both pump flow rates was similar because of spontaneous reciprocal alterations in systemic vascular resistance, that is, as perfusion flow rate declined, systemic vascular resistance increased; as perfusion flow rate increased, systemic vascular resistance declined. Under these tightly controlled conditions, pump flow variation per se exerted no effect on cerebral blood flow or cerebral metabolic rate of oxygen consumption in either group.

Efficacy of myocardial protection with hypothermic blood cardioplegia depends on oxygen.

The role of oxygen (O2) in blood cardioplegia (BCP) remains controversial. On the one hand, O2 reduces ischemic injury between BCP infusions by maintaining energy production through oxidative pathways. On the other hand, O2 carried by blood may not be released to the tissue at 4 degrees C or potentially provides substrate for deleterious O2 radical species. This study tests the hypothesis that O2 is a critical component in myocardial protection afforded by BCP. In 17 anesthetized dogs, left ventricular performance was measured by left ventricular end-systolic pressure-volume relations using the position of the end-systolic pressure-volume relation quantitated by the left ventricular midrange volume intercept at 100 mm Hg (V100) to describe performance. After 30 minutes of global normothermic ischemia, hearts were protected with multidose 4 degrees C BCP for 1 hour of arrest. Oxygen content in BCP was adjusted to 1.1 +/- 0.2 vol% (n = 7; desaturated BCP group), 4.3 +/- 0.5 vol% (n = 5; intermediate oxygenated BCP group), or 10.2 +/- 0.6 vol% (n = 5; saturated BCP group) using a membrane oxygenator interposed in the BCP circuit and aerated with an appropriate mixture of O2, nitrogen, and carbon dioxide. After 1 hour of 37 degrees C reperfusion, 3 of the 7 dogs in the desaturated BCP group failed to generate sufficient cardiac output to discontinue bypass. In the remaining 4 dogs, severe left ventricular depression caused a rightward shift in V100 from 17 +/- 4 to 47 +/- 9 mL (p = 0.02). With intermediate BCP, all hearts were weaned from bypass with marginal left ventricular depression (V100, 20 +/- 5 versus 46 +/- 16 mL; p = 0.10). In contrast, hearts protected with saturated BCP showed no significant increase in V100 (13 +/- 4 versus 24 +/- 13 mL; p = 0.23). We conclude that O2 in BCP is critical to its myocardial protective properties.

Regional function, blood flow, and oxygen utilization relations in repetitively occluded-reperfused canine myocardium.

Temporary coronary occlusion followed by reperfusion severely reduces contractile function in the involved segment. We tested whether an uncoupling exists between O2 utilization (MVO2) and systolic shortening in the ischemic-reperfused segment subjected to repetitive coronary occlusion and reperfusion. In 10 anesthetized open-chest dogs, left ventricular pressure and segment length (sonomicrometry) relations were measured in the left anterior descending (LAD, ischemic-reperfused) segment and circumflex coronary artery (nonischemic segment). Four 12-min LAD occlusions were each followed by 30 min reperfusion. MVO2 was determined in both segments by transmural blood flow (15 microns microspheres) and regional coronary arterial-venous O2 extraction after each occlusion-reperfusion period. The four occlusion-reperfusion periods did not produce necrosis by staining with triphenyltetrazolium chloride. LAD occlusion produced dyskinesis [control = 16 +/- 3.0% systolic shortening (SS) vs. -8.8 +/- 1.5%, P less than 0.0001]. The first reperfusion restored SS only to 2.3 +/- 2.0%, which progressively deteriorated to -3.9 +/- 1.1% (P less than 0.05) with subsequent occlusion-reperfusion episodes. Relative to the nonischemic segment, MVO2 in the ischemic-reperfused segment decreased by only 18% despite dyskinesis. Pressure-length analysis showed systolic stiffening during reperfusion with displacement of the passive ischemic pressure-length loop to the left. Segment work (integral of each loop) continued to be generated at 34.5% of control levels after the last occlusion-reperfusion event in contrast to the negative SS. We conclude that 1) MVO2 in the ischemic-reperfused segment without necrosis remains elevated despite severe reductions in systolic shortening, and 2) the discrepancy between systolic shortening and MVO2 is partially due to persistent development of segment work.

Nonlinearity of indexes of left ventricular performance: effects on estimation of slope and diameter axis intercepts.

The slope and diameter axis intercept (D0) of the linear indexes end-systolic pressure-diameter relation (ESPDR), maximum of the first derivative of left ventricular pressure (dP/dtmax)-end-diastolic diameter relation (dP/dtmax-Ded), and dimensional preload-recruitable stroke work relation (PRDSW) are used to describe left ventricular performance. We tested the hypothesis that nonlinearity in these indexes would preclude accurate estimation of slope and D0. In nine pentobarbital-anesthetized dogs, right heart bypass was used to obtain a wide range of pressure-minor axis diameter (sonomicrometry) points from which the three indexes were derived. For ESPDR and dP/dtmax-Ded, a nonlinear fit (y = ax2 + bx + c) approximated the data better than a linear fit, with significant nonlinearity toward the diameter axis (a = -10.28 +/- 3.42 and -111.2 +/- 26.2, respectively, P less than 0.05). Although linear D0 was significantly less than nonlinear D0, this difference was overcome by the diameter intercept at a midrange value of end-systolic pressure or dP/dtmax. PRDSW demonstrated no significant nonlinearity (a = -4.40 +/- 3.53, P = 0.86) but extrapolation to D0 demonstrated linear and nonlinear differences. We conclude that 1) ESPDR and dP/dtmax-Ded demonstrate significant nonlinearity, while PRDSW is well-approximated by a linear fit over a large range of data points; and 2) extrapolation of D0 is inaccurate in all three indexes, while a midrange intercept is independent of the model used to fit the data. Left ventricular performance may be more accurately described by linear slope and midrange diameter intercept over comparable ranges of data.

Improved lung preservation with cold air storage.

Conventional topical slush cooling limits lung transport to 4 to 6 hours. For this canine study of an alternate air cooling system, 37 canine lungs were removed: 24 were placed in plastic bags, and inserted in a Transplanthermm container at core air temperatures (n = 6 lungs each) of (A) 4 degrees C, (B) 8 degrees C, (C) 12 degrees C, and (D) 20 degrees C; 6 were stored conventionally in ice slush (E); and 7 were transplanted immediately (F). After 8 hours, the stored lungs were transplanted and the contralateral pulmonary artery was ligated. Survival, arterial oxygen tension, and extravascular lung water were monitored at 15 minutes and every hour for 4 hours. Four-hour survival was 100% in groups A, B, and F; 83% in group C, 50% in group D, and 17% in group E. The mean arterial oxygen tension at 1 hour was lower in group E (6.4 +/- 2.4 kPa) than in group A (39.8 +/- 13.2 kPa) (p = 0.0002) or in group F (42.0 +/- 16.2 kPa) (p = 0.0035). Extravascular lung water in group E was higher at 15 minutes (15.44 +/- 5.63 mL/kg) than in group A (3.76 +/- 0.63 mL/kg) (p = 0.0001) and group F (4.69 +/- 1.65 mL/kg) (p = 0.003). Cold air storage appears to provide better lung preservation than hypothermic immersion in ice slush.