Transcatheter aortic valve implantation: durability of clinical and hemodynamic outcomes beyond 3 years in a large patient cohort.

BACKGROUND: Although short- and medium-term outcomes after transcatheter aortic valve implantation are encouraging, long-term data on valve function and clinical outcomes are limited. METHODS AND RESULTS: Consecutive high-risk patients who had been declined as surgical candidates because of comorbidities but who underwent successful transcatheter aortic valve implantation with a balloon-expandable valve between January 2005 and December 2006 and survived past 30 days were assessed. Clinical, echocardiographic, and computed tomographic follow-up examinations were performed. Seventy patients who underwent successful procedures and survived longer than 30 days were evaluated at a minimum follow-up of 3 years. At a median follow-up of 3.7 years (interquartile range 3.4 to 4.3 years), survival was 57%. Survival at 1, 2, and 3 years was 81%, 74%, and 61%, respectively. Freedom from reoperation was 98.5% (1 patient with endocarditis). During this early procedural experience, 11 patients died within 30 days, and 8 procedures were unsuccessful. When these patients were included, overall survival was 51%. Transaortic pressure gradients increased from 10.0 mm Hg (interquartile range 8.0 to 12.0 mm Hg) immediately after the procedure to 12.1 mm Hg (interquartile range 8.6 to 16.0 mm Hg) after 3 years (P=0.03). Bioprosthetic valve area decreased from a mean of 1.7±0.4 cm(2) after the procedure to 1.4±0.3 cm(2) after 3 years (P<0.01). Aortic incompetence after implantation was trivial or mild in 84% of cases and remained unchanged or improved over time. There were no cases of structural valvular deterioration, stent fracture, deformation, or valve migration. CONCLUSIONS: Transcatheter aortic valve implantation demonstrates good medium- to long-term durability and preserved hemodynamic function, with no evidence of structural failure. The procedure appears to offer an adequate and lasting resolution of aortic stenosis in selected patients.

Acute hemodynamic changes after rapid intravenous bolus dosing of dexmedetomidine in pediatric heart transplant patients undergoing routine cardiac catheterization.

BACKGROUND: Dexmedetomidine is a highly selective α(2)-adrenoceptor agonist with sedative, anxiolytic, and analgesic properties that has minimal effects on respiratory drive. Its sedative and hypotensive effects are mediated via central α(2A) and imidazoline type 1 receptors while activation of peripheral α(2B)-adrenoceptors result in an increase in arterial blood pressure and systemic vascular resistance. In this randomized, prospective, clinical study, we attempted to quantify the short-term hemodynamic effects resulting from a rapid i.v. bolus administration of dexmedetomidine in pediatric cardiac transplant patients. METHODS: Twelve patients, aged 10 years or younger, weighing ≤40 kg, presenting for routine surveillance of right and left heart cardiac catheterization after cardiac transplantation were enrolled. After an inhaled or i.v. induction, the tracheas were intubated and anesthesia was maintained with 1 minimum alveolar concentration of isoflurane in room air, fentanyl (1 µg/kg), and rocuronium (1 mg/kg). At the completion of the planned cardiac catheterization, 100% oxygen was administered. After recording a set of baseline values that included heart rate (HR), systolic blood pressure, diastolic blood pressure, central venous pressure, systolic pulmonary artery pressure, diastolic pulmonary artery pressure, pulmonary artery wedge pressure, and thermodilution-based cardiac output, a rapid i.v. dexmedetomidine bolus of either 0.25 or 0.5 µg/kg was administered over 5 seconds. The hemodynamic measurements were repeated at 1 minute and 5 minutes. RESULTS: There were 6 patients in each group. Investigation suggested that systolic blood pressure, diastolic blood pressure, systolic pulmonary artery pressure, diastolic pulmonary artery pressure, pulmonary artery wedge pressure, and systemic vascular resistance all increased at 1 minute after rapid i.v. bolus for both doses and decreased significantly to near baseline for both doses by 5 minutes. The transient increase in pressures was more pronounced in the systemic system than in the pulmonary system. In the systemic system, there was a larger percent increase in the diastolic pressures than the systolic pressures. Cardiac output, central venous pressure, and pulmonary vascular resistance did not change significantly. HR decreased at 1 minute for both doses and was, within the 0.5 µg/kg group, the only hemodynamic variable still changed from baseline at the 5-minute time point. CONCLUSION: Rapid i.v. bolus administration of dexmedetomidine in this small sample of children having undergone heart transplants was clinically well tolerated, although it resulted in a transient but significant increase in systemic and pulmonary pressure and a decrease in HR. In the systemic system, there is a larger percent increase in the diastolic pressures than the systolic pressures and, furthermore, these transient increases in pressures were more pronounced in the systemic system than in the pulmonary system.

Patients' understanding of disease status and treatment plan at initial hematopoietic stem cell transplantation consultation.

Patients referred for hematopoietic stem cell transplantation (HSCT) often have knowledge deficits about their disease and overestimate their prognosis making it difficult initially to discuss potentially life-threatening transplant options. To determine patients' understanding of their disease and the adequacy of a 3-h consultation at our center, we developed a survey that measured perceived knowledge deficits of disease, prognosis, and emotional status before and after their initial consultation. Ninety nine consecutive eligible patients completed the survey. Although 76.7% claimed adequate information about their disease pre-HCST visit, 51.5 and 41.4% respectively lacked knowledge about their 1-year prognosis with and without any therapy. After the visit, 66.7% of the patients had obtained enough information to make an informed decision regarding HSCT versus 23.2% pre-visit, and a significant reduction in the need for further information was reported by 53.5% of patients (P<0.001). Patients were not overwhelmed or confused by the visit and there was a small but significant decrease in negative affect. Measures to increase patients understanding of their disease and its prognosis pre-HSCT consultation visit are warranted; however, a 3-h consultation visit provides the majority of patients with sufficient information to make an informed decision about the risk/benefit ratio of HSCT.

Autologous hematopoietic stem cell transplants that utilize total body irradiation can safely be carried out entirely on an outpatient basis.

Outpatient hematopoietic stem cell transplants (HSCT) are usually performed in patients receiving minimally mucotoxic preparative regimens; total body irradiation (TBI)-based regimens typically are excluded. To improve resource utilization and patient satisfaction, we developed a totally outpatient HSCT program for TBI regimens and compared outcomes for our first 100 such transplants to 32 performed as in-patients during the same interval, for caregiver or financial reasons. Symptoms were managed predominately with oral agents; pain management consisted of transdermal fentanyl and oral morphine solution. Except for more unmarried in-patients, the two groups were matched. Time to engraftment, severity of mucositis and transplant duration were identical for the two groups. Twenty-seven of the outpatients were admitted (median-6 days), primarily for progressing infection. Thus 92% of all transplant days were outpatient. There were no septic episodes or hospital admissions for pain management. There were no deaths to day 30 in either group and 100-day survival was identical. There was a mean cost savings of Dollars 16,000 per outpatient transplant and outpatient patient/caregiver quality of life was similar to that reported for in-patients. Patients undergoing severely mucotoxic regimens can be safely transplanted in an outpatient setting with a significant cost saving, with no increase in morbidity or mortality.

Reoperation for bioprosthetic mitral structural failure: risk assessment.

BACKGROUND: The predominant complication of bioprostheses is structural valve deterioration and the consequences of reoperation. The purpose of the study was to determine the mortality and risk assessment of that mortality for mitral bioprosthetic failure. METHODS AND RESULTS: From 1975 to 1999, 1 973 patients received a heterograft bioprosthesis in 2 152 operations. The procedures were performed with concomitant coronary artery bypass (CAB) in 694 operations and without in 1 458 operations. There were 481 reoperations for structural valve deterioration performed in 463 patients with 34 fatalities (7.1%). Of the 481 re-replacements, 67 had CAB and 414 had isolated replacement; the mortality was 11.9% (8) and 6.3% (26), respectively. Eleven predictive factors inclusive of age, concomitant CAB, urgency status, New York Heart Association (NYHA; reoperation), and year of reoperation (year periods) were considered. The mortality from 1975 to 1986 was 9.8% (6/61), from 1987 to 1992 it was 10.8% (20/185), and from 1993 to 2000 it was 3.4% (8/235) (I versus III P=0.0458, II versus III P=0.0047). The mortality by urgency status was elective/urgent 6.0% (26/436) and emergent 17.8% (8/45) (P=0.00879). The mortality was NYHA I/II 0.00% (0/37), III 5.1% (14/273), and IV 11.7% (20/171) (P=0.0069). The predictive risk factors by multivariate regression analysis were age at implant, odds ratio (OR) 0.84 (P=0.0113); age at explant, OR 1.2 (P=0.0089); urgency, OR 2.8 (P=0.0264); NYHA, OR 2.5 (P=0.015); 1975-1986 versus 1993-2000 of reoperations, OR 5.8 (P=0.0062); and 1987-19 92 versus 1993-2000, OR 4.0 (P=0.0023). For the period 1993 to 2000 of reoperations, only age at implant and age at explant were significant; NYHA class, urgency status, and concomitant CAB were not significant. CONCLUSIONS: Bioprosthetic mitral reoperative mortality can be lowered by reoperations on an elective/urgent basis in low to medium NYHA functional class. The routine evaluation of patients can achieve earlier low risk reoperative surgery.

Late results of the Warm Heart Trial: the influence of nonfatal cardiac events on late survival.

BACKGROUND: The Warm Heart Trial randomized 1732 CABG patients to receive warm or cold blood cardioplegia. In the warm cardioplegia patients, nonfatal perioperative cardiac events were significantly decreased and the mortality rate was nonsignificantly decreased (1. 4% versus 2.5%, P:=0.12). The purpose of the present study was to evaluate the late results of these trial patients. METHODS AND RESULTS: Randomization was stratified according to surgeon and urgency of the operation. Seven hundred sixty-two patients recruited from 1 of the centers were followed through the hospital clinic for late events. Late survival (including perioperative deaths) at 72 months was nonsignificantly greater in the warm cardioplegia patients (94.5+/-1.7%, mean+/-SEM) than in the cold cardioplegia patients (90.9+/-2.6%). Independent predictors of mortality by Cox proportional hazards model were redo CABG, diabetes mellitus, renal insufficiency, and increasing age. The influence of nonfatal perioperative events (perioperative myocardial infarction according to computerized ECG readings or low output syndrome as determined by an outcome committee) on late survival was also analyzed. Late survival at 84 months was significantly reduced in the group who experienced nonfatal perioperative outcomes (94.5+/-1.7% versus 84. 9+/-4.5%, P:<0.001) and remained a significant predictor after adjustment for other important variables (risk ratio 6.4, 95% CI 1. 87 to 8.73, P:<0.0001). CONCLUSIONS: Effective myocardial protection through either cold or warm blood cardioplegia is essential, because late survival is significantly reduced in patients with nonfatal perioperative cardiac outcomes.

Incidence, predictors, and significance of abnormal cardiac enzyme rise in patients treated with bypass surgery in the arterial revascularization therapies study (ARTS).

BACKGROUND: Although it has been suggested that elevation of CK-MB after percutaneous coronary intervention is associated with adverse clinical outcomes, limited data are available in the setting of coronary bypass grafting. The aim of the present study was to determine the incidence, predictors, and prognostic significance of CK-MB elevation following multivessel coronary bypass grafting (CABG). METHODS AND RESULTS: The population comprises 496 patients with multivessel coronary disease assigned to CABG in the Arterial Revascularization Therapies Study (ARTS). CK-MB was prospectively measured at 6, 12, and 18 hours after the procedure. Thirty-day and 1-year clinical follow-up were performed. Abnormal CK-MB elevation occurred in 61.9% of the patients. Patients with increased cardiac-enzyme levels after CABG were at increased risk of both death and repeat myocardial infarction within the first 30 days (P=0.001). CK-MB elevation was also independently related to late adverse outcome (P=0.009, OR=0.64). CONCLUSIONS: Increased concentrations of CK-MB, which are often dismissed as inconsequential in the setting of multivessel CABG, appear to occur very frequently and are associated with a significant increase in both repeat myocardial infarction and death beyond the immediate perioperative period.

The pulmonary venous systolic flow pulse--its origin and relationship to left atrial pressure.

OBJECTIVES: The purpose of this study was to determine the origin of the pulmonary venous systolic flow pulse using wave-intensity analysis to separate forward- and backward-going waves. BACKGROUND: The mechanism of the pulmonary venous systolic flow pulse is unclear and could be a "suction effect" due to a fall in atrial pressure (backward-going wave) or a "pushing effect" due to forward-propagation of right ventricular (RV) pressure (forward-going wave). METHODS: In eight patients during coronary surgery, pulmonary venous flow (flow probe), velocity (microsensor) and pressure (micromanometer) were recorded. We calculated wave intensity (dP x dU) as change in pulmonary venous pressure (dP) times change in velocity (dU) at 5 ms intervals. When dP x dU > 0 there is a net forward-going wave and when dP x dU < 0 there is a net backward-going wave. RESULTS: Systolic pulmonary venous flow was biphasic. When flow accelerated in early systole (S1), pulmonary venous pressure was falling, and, therefore, dP x dU was negative, -0.6 +/- 0.2 (x +/- SE) W/m2, indicating a net backward-going wave. When flow accelerated in late systole (S2), pressure was rising, and, therefore, dP x dU was positive, 0.3 +/- 0.1 W/m2, indicating a net forward-going wave. CONCLUSIONS: Pulmonary venous flow acceleration in S1 was attributed to a net backward-going wave secondary to a fall in atrial pressure. However, flow acceleration in S2 was attributed to a net forward-going wave, consistent with propagation of the RV systolic pressure pulse across the lungs. Pulmonary vein systolic flow pattern, therefore, appears to be determined by right- as well as left-sided cardiac events.

Effects of fuchsin variants in aldehyde fuchsin staining.

Aldehyde fuchsin stains pancreatic B cell granules, hypophyseal basophils, goblet cell mucins, gastric chief cells, hyaline cartilage, and elastica. Neither the chemical structure of aldehyde fuchsin nor its staining mechanism is known. This study was undertaken to clarify the role of the fuchsin component of aldehyde fuchsin in its staining reaction. The major findings of this investigation include: 1) single N-methylation of the fuchsin molecule abolishes staining of unoxidized pancreatic B cells, although it does not prevent reaction of fuchsin with paraldehyde; 2) aldehyde fuchsin is probably a Schiff base condensation product of pararosaniline and acetaldehyde; 3) a Schiff base structure alone cannot account for aldehyde fuchsin staining of unoxidized pancreatic B cells; 4) a fully potent aldehyde fuchsin is possibly a Tris-Schiff base derivative of pararosaniline.

Effect of negative pleural pressure on left ventricular hemodynamics.

Negative pleural pressure alters left ventricular (LV) function. LV volume changes have been studied in human subjects, but little is known of the hemodynamic effects. The effect of changes of pleural pressure on LV hemodynamics during a Mueller maneuver (inspiration against an obstruction) was studied in 11 subjects and during quiet, unobstructed inspiration in 3. During the Mueller maneuver, there was an initial decrease in pulmonary wedge pressure and aortic systolic pressure, almost as great as the decrease in pleural pressure. Thereafter, these pressures increased despite a sustained reduction in pleural pressure. Toward the end of the Mueller maneuver, pulmonary wedge transmural pressure averaged 31 +/- 12 mm Hg and in 6 patients large v waves developed. The increase in aortic transmural pressure averaged 30 +/- 16 mm Hg. Aortic pulse pressure decreased on the first beat from control levels of 59 +/- 21 to 47 +/- 21 (p less than 0.001) and then returned to control levels. During normal breathing in 3 subjects, studied with intraesophageal balloons, there was a similar increase in both transmural aortic and transmural pulmonary wedge pressures with a decrease in pleural pressure 6 mm Hg during inspiration. Thus, increased negative pleural pressure was associated with a marked increase in pulmonary wedge transmural pressure; the increase was approximately proportionate to the decrease in pleural pressure. It is suggested that this increase was due to increased impedance to LV ejection and to right ventricular expansion interfering with LV diastolic filling.

Computerized histologic assessment of malignant potential: a method for determining the prognosis of uveal melanomas.

The authors evaluated 50 cases of primary melanoma of the choroid and ciliary body. In each case, 100 cells were randomly selected from a single histologic slide, and on each cell computer-assisted measurements were made of 18 nuclear and nucleolar features. Means and standard deviations were calculated for each of these features in each tumor. Thirteen calculated variables (six means and seven standard deviations) were found to correlate significantly with patient mortality following enucleation. Standard deviations of statistically significant nuclear and nucleolar features demonstrated significantly greater correlation with mortality than the means of these features, thus confirming the great value of nuclear pleomorphism for predicting the malignant potential of uveal melanomas. Furthermore, when the standard deviation of the nucleolar circumference, a feature highly correlated with survival (P less than 0.00001), was combined with the measurement of the largest dimension of the tumor, linear discriminant analysis correctly predicted the clinical course of 88 per cent of cases.

Warm retrograde cardioplegia. Protection of the right ventricle in mitral valve operations.

Hypothermia is believed to be the most important aspect of successful myocardial protection with retrograde coronary sinus cardioplegia. Because nutritive capillary flow to the right ventricle and septum is thought to be diminished with retrograde perfusion, these areas of the myocardium are considered at higher risk for intraoperative deterioration without the added protection of hypothermia. Recently we introduced warm aerobic arrest as an alternative to conventional methods of myocardial protection. We present our clinical results in 37 patients with mitral valve disease (+/- aortic valve, aortic root, or coronary artery disease) who underwent various cardiac procedures for which warm blood cardioplegic solution was delivered continuously via the coronary sinus after antegrade arrest. Thirty-five of the patients were in New York Heart Association class III or IV, and 19 patients had grade 3 or grade 4 left ventricular function. Sixteen patients had pulmonary hypertension, three with suprasystemic pressures, and marked right ventricular hypertrophy. Two patients had associated left ventricular hypertrophy. Nearly all patients returned to normal sinus rhythm shortly after removal of the aortic crossclamp, and they were easily discontinued from cardiopulmonary bypass even with crossclamp times of 3 hours. The 30-day hospital mortality rate was 2.7%. The perioperative myocardial infarction rate was 5.4%, and the prevalence of low-output syndrome was 10.8%. The results suggest that retrograde coronary sinus perfusion of blood cardioplegic solution at 37 degrees C is an effective method of myocardial protection even in patients with pulmonary hypertension at high risk for right ventricular failure. Its efficacy in this circumstance does not reside in its ability to deliver hypothermia.

Assessment of three methods to reduce the influence of mathematical coupling on oxygen consumption and delivery relationships.

STUDY OBJECTIVES: To determine if oxygen consumption/oxygen delivery (VO2/DO2) relationships derived using calorimetry (which are not influenced by shared measurement error) agreed with those obtained using the pulmonary artery (PA) catheter alone. To evaluate three strategies to reduce the influence of shared measurement error to determine if agreement between the two methods could be improved. METHODS: Twenty-seven patients were studied following coronary artery bypass surgery. Calorimetric VO2, six thermodilution cardiac outputs (COs), and arterial and mixed venous oxygen content measurements were made at baseline and were repeated 30 min following dobutamine administrations of 3 microg/kg/min and 5 microg/kg/min. RESULTS: Dobutamine produced a dose-dependent increase in DO2, from 378+/-65 mL/min/m2 to 446+/-78 mL/min/m2 (p<0.01) and in both PA catheter and calorimetric-derived VO2, from 104+/-18 mL/min/Mi2 to 114+/-22 mL/min/m2 (p<0.05) and from 117+/-15 mL/min/m2 to 126+/-19 mL/min/m2 (p<0.01), respectively. Agreement was poor (bias=12%, SD=21%) between the calorimetric and PA catheter methods of determining VO2/DO2 slope. When three CO measurements were used to calculate VO2, and three separate CO measurements were used to calculate DO2, the level of agreement between the two methods improved (bias=2%, SD=15%). Increasing the number of COs resulted in a similar improvement in the level of agreement between the two methods. Weighting the slope to the observed change in DO2 was the best method to improve the level of agreement (bias=2%, SD=6% for three COs). CONCLUSIONS: To reduce the influence of shared measurement error, the best strategy to improve the measurement of VO2/DO2 slope is to maximize the change in DO2 (optimally over 100 mL/min/m2).

Warm heart surgery.

Hypothermia is widely acknowledged to be the fundamental component of myocardial protection during cardiac operations. Although it prolongs the period of ischemic arrest by reducing oxygen demands, hypothermia is associated with a number of major disadvantages, including its detrimental effects on enzymatic function, energy generation, and cellular integrity. We hypothesized that the ideal protected state of the heart would be electromechanically arrested and perfused with blood, that is, aerobic arrest. Under these conditions the fundamental need for hypothermia becomes questionable. We have developed a novel approach to myocardial protection during cardiac operations based on these concepts, in which the chemically arrested heart is perfused continuously with blood and maintained at 37 degrees C. In 121 consecutive coronary bypass procedures we have compared this approach with a historical cohort of 133 consecutive patients treated with hypothermic cardioplegia. Perioperative myocardial infarction was significantly less prevalent (1.7% versus 6.8%; p less than 0.05) in the warm cardioplegic group, as was the use of the intraaortic balloon pump (0.9% versus 9.0%; p less than 0.005) and the prevalence of low output syndrome (13.5% versus 3.3%; p less than 0.005). Cardiac output immediately after bypass was significantly higher than before bypass (3.1 +/- 0.9 versus 4.9 +/- 1.0 L/min; p less than 0.001) only in the warm cardioplegia group. Furthermore, the heartbeat in 99.2% of patients treated with continuous warm cardioplegia converted to normal sinus rhythm spontaneously after removal of the aortic crossclamp compared with only 10.5% of the hypothermic group. The time from removal of the aortic crossclamp to discontinuation of cardiopulmonary bypass (i.e., reperfusion time) was significantly shorter in the warm cardioplegia group (11 +/- 4.3 versus 27 +/- 5.6 minutes; p less than 0.001). Our results suggest that continuous normothermic blood cardioplegia is safe and effective. Conceptually, this represents a new approach to the problem of maintaining excellent myocardial preservation during cardiac operations.

Automated distal coronary bypass with a novel magnetic coupler (MVP system).

OBJECTIVE: We sought to assess the feasibility of performing sutureless distal coronary artery bypass anastomoses with a novel magnetic coupling device. METHODS: From May 2000 to April 2001, single-vessel side-to-side coronary artery bypass grafting on a beating heart was performed in 39 domestic white pigs (35-60 kg) without the use of mechanical stabilization, shunts, or perfusion bridges. Animals were divided into 2 groups. Seventeen pigs underwent right internal thoracic artery to right coronary artery bypass grafting through a median sternotomy (group 1) with a novel magnetic vascular positioning system (MVP system; Ventrica, Inc, Fremont, Calif). Twenty-two pigs underwent left internal thoracic artery to left anterior descending artery grafting with the MVP anastomotic device through a left anterior minithoracotomy (group 2). This system consists of 2 pairs of elliptical magnetic implants and a deployment device. One pair of magnets forms the anastomotic docking port within the graft; the other pair forms an identical anastomotic docking port within the target vessel. The anastomosis is created when the 2 docking ports magnetically couple. Anastomotic patency was evaluated by means of angiography during the first postoperative week and at 1 month. Histologic studies were performed at different time points as late as 6 months. RESULTS: Right internal thoracic artery to right coronary artery anastomoses and left internal thoracic artery to left anterior descending artery anastomoses were successfully performed with the system in all animals. The self-adherent and self-aligning properties of the implants allowed for immediate and secure approximation of the arteries (total anastomotic time between 2-3 minutes). Anastomoses were constructed without a stabilization platform. Five nondevice-related deaths occurred postoperatively. One-week angiography, performed in 35 surviving animals, showed a patent graft and anastomosis in all cases. The patency rate at 1 month was 97% (33/34). Histologic studies as late as 6 months demonstrated neointimal coverage of the magnets without any significant luminal obstruction. Histology also confirmed the presence of viable tissue between magnets. CONCLUSION: The MVP anastomotic system uses magnetic force to create rapid and secure distal coronary artery anastomoses, which might facilitate minimally invasive and totally endoscopic coronary artery bypass surgery.

Normothermic ischemia in coronary revascularization.

Warm heart surgery-continuous perfusion with normothermic blood cardioplegia-was introduced as an alternative to conventional intermittent hypothermic perfusion for myocardial protection. Interruption of global coronary flow, however, greatly facilitates the performance of distal coronary anastomoses and is the method that has evolved with many surgeons using warm blood cardioplegia for coronary revascularization. We present results (mean +/- SD) in 720 patients undergoing coronary bypass surgery protected with intermittent warm blood cardioplegia and exposed to normothermic ischemia but with electromechanical arrest. An average of 3.2 +/- 0.9 grafts were constructed per case with an average aortic cross clamp time of 61.8 +/- 22.2 minutes. Cardioplegia was interrupted a total of 28.5 +/- 12.4 min per operation. The percent time off cardioplegia (PTOC) expressed as a proportion of the cross clamp was 48.2 + 18.6%. The longest single time off cardioplegia (LTOC) was 11.4 +/- 4.0 min per patient. Calculated mean cardioplegia delivery during the cross clamp period was 75 ml/min. PTOC and LTOC were divided into quartiles (PTOC: < 36, 36-49, 50-62, > 62%; LTOC: < 10, 10-11, 12-13, > 13 min) and related to prespecified composite outcome of mortality, enzymatic myocardial infarct and low output syndrome. PTOC was protective (event rate/quartile 16.1%, 17.2%, 9.4%, 10.6%, p = 0.07) and longer LTOC (event rate/quartile 13.5%, 10.3%, 10.9%, 19.0%, p = 0.046) borderline harmful. The data suggest that when necessary multiple periods of normothermic myocardial ischemia in the presence of electromechanical arrest are well tolerated and potentially protective provided that any single ischemic interval is < 13 min.

Mechanisms of gas exchange with different gases during constant-flow ventilation.

To investigate the mechanisms responsible for the difference in gas exchange during constant-flow ventilation (CFV) when using gases with different physical properties, we used mixtures of 70% N2-30% O2 (N2-O2) and 70% He-30% O2 (He-O2) as the insufflating gases in 12 dogs. All dogs but one had higher arterial PCO2 (PaCO2) with He-O2 compared with N2-O2. At a flow of 0.37 +/- 0.12 l/s, the mean PaCO2's with N2-O2 and He-O2 were 41.3 +/- 13.9 and 53.7 +/- 20.3 Torr, respectively (P less than 0.01); at a flow rate of 0.84 +/- 0.17 l/s, the mean PaCO2's were 29.1 +/- 11.3 and 35.3 +/- 13.6 Torr, respectively (P less than 0.01). The chest was then opened to alter the apposition between heart and the lungs, thereby reducing the extent of cardiogenic oscillations by 58.4 +/- 18.4%. This intervention did not significantly alter the difference in PaCO2 between N2-O2 and He-O2 from that observed in the intact animals, although the individual PaCO2 values for each gas mixture did increase. When the PaCO2 was plotted against stagnation pressure (rho V2), the difference in PaCO2 between N2-O2 and He-O2 was nearly abolished in both the closed- and open-chest animals. These findings suggest that the different PaCO2's obtained by insufflating gases with different physical properties at a fixed flow rate, catheter position, and lung volume result mainly from a difference in the properties of the jet.

Contribution of cardiogenic oscillations to gas exchange in constant-flow ventilation.

The contribution of cardiogenic oscillations to gas exchange during constant-flow ventilation was examined in 11 dogs. With the use of two variations of cardiopulmonary bypass to maintain the systemic and pulmonary circulation, the influence of cardiogenic oscillations was removed by arresting the heart. Cardiac arrest by ventricular fibrillation was associated with a mean decrease in alveolar ventilation of 43% in five dogs on right and left heart bypass. However, successful defibrillation and return of the prearrest level of alveolar ventilation could not be achieved; thus we studied six dogs on left heart bypass. Alveolar ventilation decreased an average of 37% with cardiac arrest, and defibrillation resulted in a return of alveolar ventilation to 81% of the prearrest value. These results are consistent with previous predictions that cardiogenic oscillations are an important mechanism of gas transport during constant-flow ventilation.

Modified Cabrol shunt for control of hemorrhage in repair of type A dissection of the aorta.

A technique of modifying the Cabrol shunt using preserved bovine pericardium and a patch of autologous pericardium to deal with postoperative hemorrhage from an ascending aortic operation is described. A fistula to the right atrium was created for autotransfusion. This simple technique is very useful for dealing with the catastrophic complication of such postoperative hemorrhage.

Warm heart surgery and results of operation for recent myocardial infarction.

Revascularization procedures after recent myocardial infarction are associated with higher mortality and morbidity compared with elective coronary artery bypass grafting. Traditional methods of myocardial protection impose a further ischemic insult on already compromised myocardium. Continuous cold blood cardioplegia may eliminate ischemia but may still leave the heart anaerobic. Theoretically, warm aerobic arrest addresses both of these issues and may become an attractive alternative to standard hypothermic ischemic arrest in this setting. In 115 nonrandomized patients undergoing coronary artery bypass grafting within 6 hours to 7 days of an acute myocardial infarction, myocardial protection was provided with continuous cold (4 degrees C) or continuous warm (37 degrees C) blood cardioplegia. Fifty-one patients (after 1988) protected with warm blood cardioplegia were compared with a historical cohort of 64 patients (before 1988) protected with cold blood cardioplegia. Results indicate that the warm cardioplegia group had no mortality versus 10.9% for the cold group (p less than 0.05), a myocardial infarction rate of 2.0% in the warm versus 9.3% in the cold group, and use of intraaortic balloon pump of 0% versus 12.5%, respectively (p less than 0.05). It is concluded that continuous warm aerobic arrest may minimize ischemia and anaerobic metabolism during the operative procedure, and may be of benefit to patients who have a limited tolerance to ischemic insult.