Extra-corporeal membrane oxygenation for the post-cardiotomy patient.

Extra-corporeal membrane oxygenation remains the last resort in keeping patients alive in those with profound cardiogenic shock following percutaneous interventions or open surgery on the heart. No guidelines exist on the management of patients on such a device despite a high mortality. We attempt to highlight some universal principles that would be relevant to the current practice of those exposed to this challenging field.

The effect of deep hypothermia on the human pulmonary circulation.

OBJECTIVE: Acute rises in pulmonary artery pressures following complex cardiac surgery are associated with high morbidity and mortality. We hypothesised that periods of deep hypothermia predispose to elevated pulmonary pressures upon rewarming. We investigated the effect of this hypothermic preconditioning on isolated human pulmonary arteries and isolated perfused lungs. METHODS: Isometric tension was measured in human pulmonary artery rings (n=24). We assessed the constriction and dilation of these arteries at 37 °C and 17 °C. Isolated perfused human lung models consisted of lobes ventilated via a bronchial cannula and perfused with Krebs via a pulmonary artery cannula. Bronchial and pulmonary artery pressures were recorded. We investigated the effect of temperature using a heat exchanger. RESULTS: Rewarming from 17 °C to 37 °C caused a 1.3 fold increase in resting tension (p<0.05). Arteries constricted 8.6 times greater to 30 nM KCl, constricted 17 times greater to 1 nM Endothelin-1 and dilated 30.3 times greater to 100 µM SNP at 37 °C than at 17 °C (p<0.005). No difference was observed in the responses of arteries originally maintained at 37 °C compared to those arteries maintained at 17 °C and rewarmed to 37 °C. Hypothermia blunted the increase in pulmonary artery pressures to stimulants such as potassium chloride as well as to H-R but did not precondition arteries to higher pulmonary artery pressures upon re-warming. CONCLUSIONS: Deep hypothermia reduces the responsiveness of human pulmonary arteries but does not, however, precondition an exaggerated response to vasoactive agents upon re-warming.

Complex aortic surgery in a regional center in the United Kingdom. Should the United Kingdom now adopt a United States-style supercenter model?

BACKGROUND: The United States has established aortic supercenters, which have demonstrated clear improvements in the short-term and long-term outcomes after surgery on the thoracic aorta. This model of care does not exist in the United Kingdom. We have looked at our recent experience of emergency and elective thoracic aortic surgery and describe and compare our operative outcomes and 10-year survival with other regional centers and supercenters worldwide. METHODS: This was a retrospective analysis of data collected prospectively from our cardiac database on patients who underwent surgery on the thoracic aorta (n=318) between November 1999 and November 2012. The outcome measures were adjusted operative mortality, postoperative complications, and long-term survival. RESULTS: Type A dissection was carried out on 23.90% of the patients and 76.10% had surgery on the aortic root and thoracic aorta for nondissection. The mean age of the patients was 62.21±14.1 years. The mean logistic EuroSCORE was 26 in the dissection group and 19 in the nondissection group. Hospital mortality was significantly greater (P<.05) in the dissection group compared with the nondissection group (23.7% vs 12.8%). Survival after dissection and nondissection surgery was 66.3%±5.6% versus 77.4%±2.8%, respectively, at 3 years, 63.9%±5.9% versus 71.8%±3.2% at 5 years, and 53.7%±7.4% versus 47.1%±6.0% at 10 years. CONCLUSIONS: Our outcomes are comparable with other regional centers worldwide; however, they are not as good as those reported from the aortic supercenters. There should be continued impetus regarding the establishment of thoracic aortic surgery guidelines and specialist aortic centers in the United Kingdom.

Hyperoxic vasoconstriction of human pulmonary arteries: a novel insight into acute ventricular septal defects.

Objectives. Acute rises in pulmonary artery pressures following postinfarction ventricular septal defects present a challenge. We hypothesised that the abnormally high oxygen content exposure to the pulmonary arteries may be a factor. We investigated the contractile responses of human pulmonary arteries to changes in oxygen tension. Methods. Isometric tension was measured in large and medium sized pulmonary artery rings obtained from lung resections for patients with bronchial carcinoma (n = 30). Fresh rings were mounted in organ baths bubbled under basal conditions with hyperoxic or normoxic gas mixes and the gas tensions varied during the experiment. We studied whether voltage-gated calcium channels and nitric oxide signalling had any role in responses to oxygen changes. Results. Hypoxia caused a net mean relaxation of 18.1% ± 15.5 (P < 0.005) from hyperoxia. Subsequent hyperoxia caused a contraction of 19.2% ± 13.5 (P < 0.005). Arteries maintained in normoxia responded to hyperoxia with a mean constriction of 14.8% ± 3.9 (P < 0.005). Nifedipine inhibited the vasoconstrictive response (P < 0.05) whilst L-NAME had no effect on any hypoxic vasodilatory response. Conclusions. We demonstrate that hyperoxia leads to vasoconstriction in human pulmonary arteries. The mechanism appears to be dependent on voltage-gated calcium channels. Hyperoxic vasoconstriction may contribute to acute rises in pulmonary artery pressures.

Changing operative characteristics of patients undergoing operations for coronary artery disease: impact on early outcomes.

BACKGROUND: Aggressive nonsurgical revascularization results in high-risk patients presenting for operation at a later stage of coronary artery disease (CAD). This study investigated the effect of temporal changes in operative characteristics on outcomes of surgical revascularization. METHODS: We compared preoperative, intraoperative, and postoperative variables of 5633 patients who underwent surgical revascularization for CAD between April 1998 and January 2007, divided into early (1998 to 2002, n = 2746) and late (2004 to 2007, n = 2887) eras. End points were major adverse outcomes (postoperative myocardial infarction, stroke, new dialysis) and operative mortality. RESULTS: Median age (66 vs 68 years, p < 0.0001), prevalence of left ventricular systolic dysfunction, left main stem disease, prior angioplasty, diabetes mellitus, concomitant valve operation, and aprotinin use increased steadily over time. Severe symptoms, nonelective operations, mean number of grafts, postoperative bleeding, reopening for bleeding, and blood transfusion declined. Major complications were evenly distributed between the eras. Operative mortality for isolated coronary artery bypass grafting did not change (2.0% vs 1.8% p = 0.62) despite increasing operative risk (p < 0.0001); there was a 100% reduction in the absolute risk (110% to 210%) over time. The markers for operative difficulties, such as longer bypass times, were determinants of operative mortality and, in addition to other predictors like age and left ventricular systolic dysfunction, were more prevalent in the late era. CONCLUSIONS: Coronary operations are increasingly performed in higher-risk patients; however, surgical revascularization is nearly twice as safe in current practice compared with a decade ago.

Early and late survival after surgical revascularization for ischemic ventricular fibrillation/tachycardia.

BACKGROUND: Ischemic ventricular fibrillation/tachycardia (VF/VT) treated by myocardial revascularization, often with an implanted cardioverter defibrillator, prevents sudden cardiac death. Early series have suggested that recurrent VF/VT threatens survival even after treatment. As late outcome is unknown, we sought to determine if the early survival benefit is sustained. METHODS: From January 1999 through January 2007, 93 consecutive patients (75 male, 81%) presented with ischemic VF/VT; 21% survived cardiac arrest and underwent coronary artery bypass graft surgery at our institution. We analyzed their early and late survival. RESULTS: Median age was 66 years (range, 44 to 88). Clinical presentation included class III/IV angina (46%), controlled heart failure (43%), prior myocardial infarction (68%), left ventricular ejection fraction less than 0.30 (23%) and 0.30 to 0.50 (35%), left main stem disease (24%), and triple-vessel disease (67%). Surgical revascularization, mostly nonelective (urgent 73%, emergency 7%), was combined with aortic valve replacement in 5 patients and left ventricular pseudoaneurysm repair in 3. Ischemic territories and mean number of diseased coronaries (2.6) corresponded to the grafted territories and average number of grafts (2.5). Operative mortality was 6.5% (n = 6, median EuroSCORE [European System for Cardiac Operative Risk Evaluation] predicted mortality 9). Recurrent VF/VT occurred early postoperatively in 21 patients (24%). All patients had electrophysiologic studies postoperatively and 40% received an implanted cardioverter defibrillator. Of 12 late deaths (16%) at follow-up extending to 8 years, 4 (33%) were due to cardiac causes. Five-year survival was 88%, equivalent to that (83% to 85%) reported for patients with sinus rhythm preoperatively. CONCLUSIONS: Complete myocardial revascularization for ischemic VF/VT yields excellent early and late results; 5-year survival is comparable to that of patients with preoperative sinus rhythm.

Intensive care unit readmission after elective coronary artery bypass grafting.

Prospective data of 3,120 consecutive patients who had elective coronary artery bypass were analyzed to identify patient profile, cost, outcome and predictors of those readmitted to the intensive care unit. Group A (n=3,002) had a single intensive care unit admission and group B (n=118) were readmitted within 30 days after surgery. Parsonnet score, EuroSCORE, age, body mass index, chronic obstructive airway disease, peripheral vascular disease, renal dysfunction, unstable angina, congestive cardiac failure, and poor left ventricular function were higher in group B. Bypass and crossclamp times were longer, and the prevalence of inotropic and balloon pump support, arrhythmias, myocardial infarction, re-exploration, blood loss and transfusion, cerebrovascular accident, wound infection, sternal dehiscence, and multisystem failure were higher in group B. Despite a 4-fold increase in cost of care, the mortality rate (32.4%) of patients readmitted to intensive care was 23-times higher than routine patients (1.4%). Crossclamp time>80 min, Parsonnet score>10, EuroSCORE>9, sternal dehiscence, ventricular arrhythmias, and renal failure predicted readmission.