F.Neil McKenzie

Off-pump surgery decreases postoperative complications and resource utilization in the elderly

BACKGROUND Bypass surgery in the elderly (age >70 years) has increased mortality and morbidity, which may be a consequence of cardiopulmonary bypass. We compare the outcomes of a cohort of elderly off-pump coronary artery bypass (OPCAB) patients with elderly conventional coronary artery bypass grafting (CABG) patients. METHODS Chart and provincial cardiac care registry data were reviewed for 30 consecutive elderly OPCAB patients (age 74.7 +/- 4.2 years) and 60 consecutive CABG patients (age 74.9 +/- 4.1 years, p = 0.82) with similar risk factor profiles: Parsonnet score 17.2 +/- 8.1 (OPCAB) versus 15.6 +/- 6.5 (CABG), p = 0.31; and Ontario provincial acuity index 4.5 +/- 1.9 (OPCAB) versus 4.3 +/- 2.0 (CABG), p = 0.65. RESULTS Mean hospital stay was 6.3 +/- 1.8 days for OPCAB patients and 7.7 +/- 3.9 days for CABG patients (p < 0.05). Average intensive care unit stay was 24.0 +/- 10.9 h for OPCAB patients versus 36.6 +/- 33.5 h for CABG patients (p < 0.05). Atrial fibrillation occurred in 10.0% of OPCAB patients and 28.3% of CABG patients (p < 0.05). Low output syndrome was observed in 10% of OPCAB patients and 31.7% of CABG patients (p < 0.05). Cost was reduced by

Aprotinin significantly decreases bleeding and transfusion requirements in patients receiving aspirin and undergoing cardiac operations

1,082 (Canadian) per patient in the OPCAB group. Postoperative OPCAB graft analysis showed 100% patency. CONCLUSIONS OPCAB is safe in the geriatric population and significantly reduces postoperative morbidity and cost.

The role of donor age and ischemic time on survival following orthotopic heart transplantation

BACKGROUND Patients with heart disease are frequently maintained on a regimen of aspirin because of its ability to decrease thrombotic complications and reduce the prevalence of unstable angina and myocardial infarction. Aspirin-induced platelet acetylation also increases bleeding caused by impairment of platelet function during cardiac surgery. METHODS Between October 1990 and November 1991 this double-blind, randomized, placebo-controlled, parallel group interventional study examined the efficacy of high-dose aprotinin administration (up to 7 million KIU) to decrease blood loss and transfusion requirements in patients receiving aspirin within 48 hours of undergoing coronary bypass or valvular heart operations. Primary outcome measures in this study were total volume of blood loss (intraoperative blood loss plus postoperative chest tube drainage) and volume of transfusion during hospitalization. RESULTS Patients treated with aprotinin (n = 29) had significantly lower total blood loss (1409 +/- 232 ml versus 2765 +/- 248 ml; p = 0.0002), intraoperative blood loss (503 +/- 53 ml versus 1055 +/- 199 ml; p = 0.0001), postoperative blood loss (906 +/- 204 ml versus 1710 +/- 202 ml; p = 0.0074), and prevalence of transfusion (59% versus 88% of patients; p = 0.016) than the placebo group (n = 25). The prevalence of complications including myocardial infarction was similar in the two groups. CONCLUSIONS High-dose aprotinin significantly reduces blood loss and red blood cell transfusions in patients receiving aspirin who undergo cardiac operations.

Frequency of angiographic detection and quantitative assessment of coronary arterial disease one and three years after cardiac transplantation

BACKGROUND The advances in immunotherapy, along with a liberalization of eligibility criteria have contributed significantly to the ever increasing demand for donor organs. In an attempt to expand the donor pool, transplant programs are now accepting older donors as well as donors from more remote areas. The purpose of this study is to determine the effect of donor age and organ ischemic time on survival following orthotopic heart transplantation (OHT). METHODS From April 1981 to December 1996 372 adult patients underwent OHT at the University of Western Ontario. Cox proportional hazards models were used to identify predictors of outcome. Variables affecting survival were then entered into a stepwise logistic regression model to develop probability models for 30-day- and 1-year-mortality. RESULTS The mean age of the recipient population was 45.6 +/- 12.3 years (range 18-64 years: 54 < or = 30; 237 were 31-55; 91 > 56 years). The majority (329 patients, 86.1%) were male and the most common indications for OHT were ischemic (n = 180) and idiopathic (n = 171) cardiomyopathy. Total ischemic time (TIT) was 202.4 +/- 84.5 minutes (range 47-457 minutes). In 86 donors TIT was under 2 hours while it was between 2 and 4 hours in 168, and more than 4 hours in 128 donors. Actuarial survival was 80%, 73%, and 55% at 1, 5, and 10 years respectively. By Cox proportional hazards models, recipient status (Status I-II vs III-IV; risk ratio 1.75; p = 0.003) and donor age, examined as either a continuous or categorical variable ([age < 35 vs > or = 35; risk ratio 1.98; p < 0.001], [age < 50 vs > or = 50; risk ratio 2.20; p < 0.001], [age < 35 vs 35-49 versus > or = 50; risk ratio 1.83; p < 0.001]), were the only predictors of operative mortality. In this analysis, total graft ischemic time had no effect on survival. However, using the Kaplan-Meier method followed by Mantel-Cox logrank analysis, ischemic time did have a significant effect on survival if donor age was > 50 years (p = 0.009). By stepwise logistic regression analysis, a probability model for survival was then developed based on donor age, the interaction between donor age and ischemic time, and patient status. CONCLUSIONS Improvements in myocardial preservation and peri-operative management may allow for the safe utilization of donor organs with prolonged ischemic times. Older donors are associated with decreased peri-operative and long-term survival following. OHT, particularly if graft ischemic time exceeds 240 minutes and if these donor hearts are transplanted into urgent (Status III-IV) recipients.

Pharmacologic EEG suppression during cardiopulmonary bypass: cerebral hemodynamic and metabolic effects of thiopental or isoflurane during hypothermia and normothermia

The reported high incidence of coronary atherosclerosis in many transplant series led us to critically review our experience in 83 patients who have had selective coronary angiography at greater than or equal to 1 years after transplantation. Angiograms were reviewed for evidence of coronary vascular disease, and quantitative analysis of multiple coronary artery segments was performed in serial films. Qualitative analysis revealed only 3 of 83 patients with any angiographic abnormality at follow-up, 1 with minimal luminal irregularities in the right coronary artery at 1 year, a second with a 50% diameter stenosis of the proximal left anterior descending artery and minimal irregularity of the proximal circumflex artery at 1 year and a third patient who developed a new 30% diameter eccentric proximal right coronary artery stenosis at 3-year follow-up. The cumulative incidence of graft vascular disease assessed angiographically was therefore 2% at 1 year and 4% at 3 years. Quantitative analysis, however, showed a significant decrease in coronary artery luminal diameter over time. The mean left main coronary artery diameter decreased from 5.4 +/- 0.9 mm at 1 year to 4.7 +/- 0.8 mm at 3 years (p = 0.0007).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic profiles at rest and during supine exercise after orthotopic cardiac transplantation

We have determined the effects of thiopental or isoflurane upon cerebral blood flow (CBF) and the cerebral metabolic rate for oxygen (CMRO2) when these agents are used in sufficient dose to attain a deep burst suppression pattern on the electroencephalogram (EEG) during hypothermic and normothermic cardiopulmonary bypass (CPB). Thirty-one patients undergoing coronary artery bypass graft surgery were anesthetized with fentanyl 0.1 mg.kg−1, and were randomly allocated to one of three groups: control (no further anesthetics during bypass and continuous EEG activity), thiopental treatment (EEG suppression), or isoflurane treatment (EEG suppression). Hypothermia (25–29° C) was routinely induced at onset of nonpulsatile cardiopulmonary bypass. In the treatment groups, thiopental or isoflurane were used during bypass to achieve a deep burst suppression pattern. Cerebral blood flow and cerebral metabolic rate for oxygen were determined during hypothermia and upon rewarming to normothermia (37° C). Pharmacologic EEG suppression with either isoflurane or thiopental was associated with lower cerebral metabolic rate than control values during both hypothermic and normothermic bypass. However, only thiopental-in-duced EEG suppression was associated with lower cerebral blood flow than control. Cerebral blood flow during isoflurane-induced EEG suppression was similar to control values in spite of the reduced cerebral metabolic rate.

Cardiac dynamics during supine exercise in cyclosporine-treated orthotopic heart transplant recipients: Assessment by radionuclide angiography

To characterize the spectrum of hemodynamic findings after orthotopic cardiac transplantation, 20 healthy heart transplant recipients with no evidence of cardiac dysfunction by noninvasive testing were studied for 1 to 51 months (mean 15) following surgery. After routine endomyocardial biopsy, right-sided heart pressures and thermodilution cardiac outputs were measured at rest (supine) and during symptom-limited, graded supine exercise. In addition, the effect of respiration on right atrial pressures and waveforms was determined at rest (supine, legs down), and after passive leg raising (volume loading). During exercise, striking increases of pulmonary artery, pulmonary artery wedge and right atrial pressures were seen. The mean pulmonary artery pressure rose 45% during the first stage of exercise (p less than 0.001) and by peak exercise it had increased 87% above resting values. The pulmonary artery wedge pressure increased significantly with passive leg elevation (p less than 0.001) and during the first stage of exercise rose 61% above baseline values. By peak exercise the mean pulmonary artery wedge pressure was more than double the resting value. Similarly, the right atrial mean pressure increased significantly (p less than 0.001) with passive leg elevation and nearly tripled at peak exercise. All values promptly returned to near baseline after exercise. The cardiac output increased 98% during exercise. During early exercise, the rise in cardiac output was mediated primarily by an increase in stroke volume. At rest, there was an abnormal response in right atrial mean pressure during slow deep inspiration in 7 individuals with legs down and in 12 after passive leg elevation (volume loading), including 4 of 10 patients studied beyond 1 year.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of robot-assisted versus manually constructed endoscopic coronary anastomosis.

The mechanisms by which the denervated heart responds to supine exercise were assessed by equilibrium gated radionuclide angiography in 18 cardiac transplant recipients 1 to 25 months (mean 11) after surgery. Results were compared with those in 15 normal subjects. Exercise duration among transplant recipients did not differ significantly from that in normal subjects. The heart rate at rest in transplant patients was 30% higher than in normal volunteers. Heart rate increased only 3% between rest and the first stage of exercise in transplant recipients compared with a 37% increase in the normal group (p less than 0.001). Cardiac output at rest was similar in both groups although the rate of rise of cardiac output and peak cardiac output were significantly lower among the transplant recipients. In early exercise, the means by which cardiac output increased in the transplant patients differed significantly from normal. In the transplant recipients, the left ventricular end-diastolic volume index increased 14% compared with a decrease of 2% in normal subjects (p less than 0.001) during the first stage of exercise. At the same time, the end-systolic volume index increased 6% in the transplant group but decreased 11% in normal subjects (p less than 0.001). These changes resulted in an overall increase in stroke volume by 20% in the transplant group compared with only a slight increase (+3%) in normal subjects (p less than 0.001) during the first stage of exercise. Among transplant recipients, the stroke volume index plateaued after the first stage of exercise, which, in combination with the blunted chronotropic response, resulted in a peak cardiac index 25% lower than that in normal subjects (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Evolution of heart rate responsiveness after orthotopic cardiac transplantation

BACKGROUND New technology has enabled surgeons to attempt totally endoscopic coronary artery bypass grafting. Our purpose was to compare three different techniques of totally endoscopic anastomosis using a porcine animal model. METHODS Porcine hearts were excised and the right coronary artery was dissected free for use as an arterial graft. The hearts were placed in a human thoracic model and an endoscopic arterial anastomosis between the free right coronary artery and the left anterior descending coronary artery was performed using one of the following: (1) two-dimensional visualization with straight endoscopic instruments (n = 8); (2) three-dimensional head-mounted visualization with curved endoscopic instruments (n = 7); or (3) three-dimensional visualization with robotic telemanipulation (n = 8). Pathologic analysis of suture placement, vessel trauma, and patency was performed. Anastomoses were graded according to quality, ease, and patency using a seven-point Likert scale (1 = excellent, 7 = very poor). RESULTS Endoscopic anastomotic ease and quality were significantly improved when three-dimensional visualization and curved endoscopic instruments were employed. Telemanipulation enhanced the process and provided the best operative results with regard to time required to construct the anastomosis, as well as ease and quality. CONCLUSIONS Totally endoscopic anastomosis is feasible using currently available technology. Three-dimensional visualization and robotic telemanipulation significantly facilitate anastomosis construction and will likely benefit clinical operative outcome.

Safety and cost-effectiveness of MIDCABG in high-risk CABG patients

Although anatomic reinnervation of the donor heart is unlikely after transplantation, individual subjects have been noted to show near physiologic heart rate (HR) responses to exercise. To assess development of this phenomenon, we studied HR changes in response to orthostasis and treadmill exercise in 52 orthotopic cardiac transplant recipients grouped according to time after transplantation. In group 1 (2.0 +/- 0.9 months), no significant increase in HR was seen up to 100 cardiac cycles after standing. A maximal acceleration of 4.0 +/- 3.8 beats was seen within 100 cardiac cycles after standing in group 2 (15.8 +/- 5.6 months). Patients in group 3 (42.4 +/- 12.4 months) showed significant cardioacceleration by 5 cardiac cycles after standing to a maximum of 10.7 +/- 5.8 beats/min within the first 100 cardiac cycles. During exercise, HR increased more rapidly during the first minute in group 3 compared with group 1 (p less than 0.01). After exercise, HR continued to increase in group 1 but decreased rapidly in the other groups, most notably group 3 (-26.5 +/- 16.5 by 2 minutes, p less than 0.0001 vs groups 1 and 2). These data indicate development of functional reinnervation after orthotopic heart transplantation. The phenomenon of early acceleration of the HR after orthostasis and rapid deceleration after exercise in transplant recipients implies a local cardiac mechanism rather than response to circulating catecholamines.