Stefan Thelin

Thoracic Aortic Aneurysm and Dissection Increasing Prevalence and Improved Outcomes Reported in a Nationwide Population-Based Study of More Than 14 000 Cases From 1987 to 2002

Background— Current knowledge of prevalence, incidence, and survival in thoracic aortic diseases (aneurysm and dissection) is based on small studies from a dated era of treatment and diagnostic procedures. The objective of the present study was to reappraise epidemiology and long-term outcomes in subjects with thoracic aortic disease in a large contemporary population. Methods and Results— All subjects with thoracic aortic aneurysm or dissection identified in Swedish national healthcare registers from 1987 to 2002 were included in the present study. Of 14 229 individuals with thoracic aortic disease, 11 039 (78%) were diagnosed before death. Incidence of thoracic aortic disease rose by 52% in men and by 28% in women to reach 16.3 per 100 000 per year and 9.1 per 100 000 per year, respectively. Operations increased 7-fold in men and 15-fold in women over time. Of the 2455 patients who underwent operation, 389 (16%) died within 30 days, with older age and thoracic aortic rupture as risk factors. In Cox analysis, increasing age was the only variable associated with long-term mortality. Both short- and long-term mortality improved over time. In patients who underwent operation, actuarial survival (95% CI) at 1, 5, and 10 years was 92% (91% to 93%), 77% (75% to 80%), and 57% (53% to 61%), respectively. The cumulative incidence of thoracic aortic reoperations was 7.8% at 10 years. Conclusions— The prevalence and incidence of thoracic aortic disease was higher than previously reported and increasing. The annual number of operations increased substantially. Surgical (30-day) and long-term survival improved significantly over time to form a growing cohort of patients needing counseling, management decisions, operations, and extended postoperative surveillance.

Atelectasis is a major cause of hypoxemia and shunt after cardiopulmonary bypass: an experimental study.

Background: Respiratory failure after cardiopulmonary bypass (CPB) remains a major complication after cardiac surgery. The authors tested the hypothesis that atelectasis is an important factor responsible for the increase in intrapulmonary shunt after CPB. Methods: Six pigs received standard CPB (bypass group). Six other pigs had the same surgery but without CPB (sternotomy group). Another six pigs were anesthetized for the same duration but without any surgery (control group). The ventilation‐perfusion distribution was measured with the inert gases technique, extravascular lung water was quantified by the double‐indicator distribution technique, and atelectasis was analyzed by computed tomography. Results: Intrapulmonary shunt increased markedly after bypass but was unchanged over time in the control group (17.9 +/‐ 6.2% vs. 3.5 +/‐ 1.2%; P < 0.0001). Shunt also increased in the sternotomy group (10 +/‐ 2.6%; P < 0.01 compared with baseline) but was significantly lower than in the bypass group (P < 0.01). Extravascular lung water was not significantly altered in any group. The pigs in the bypass group showed extensive atelectasis (32.3 +/‐ 28.7%), which was significantly larger than in the two other groups. The pigs in the sternotomy group showed less atelectasis (4.1 +/‐ 1.9%) but still more (P < 0.05) than the controls (1.1 +/‐ 1.6%). There was good correlation between shunt and atelectasis when all data were pooled (R2 = 0.67; P < 0.0001). Conclusions: Atelectasis is produced to a much larger extent after CPB than after anesthesia alone or with sternotomy and it explains most of the marked post‐CPB increase in shunt and hypoxemia. Surgery per se contributes to a lesser extent to postoperative atelectasis and gas exchange impairment.

Monocyte tissue factor expression, cell activation, and thrombin formation during cardiopulmonary bypass : A clinical study

OBJECTIVES Cardiopulmonary bypass is associated with extensive thrombin generation and cell activation. Our main hypothesis in this study was that the expression of tissue factor on circulating monocytes contributes to the formation of thrombin. METHODS Markers of activation of the coagulation cascade and cell activation were measured in 26 patients undergoing elective heart operations randomized to the use of heparin-coated (Duraflo II, n = 13) or standard cardiopulmonary bypass circuits (n = 13). RESULTS Thrombin generation, measured as the thrombin-antithrombin complex, increased considerably during cardiopulmonary bypass with peak levels 3 hours afterward and with remaining elevation 20 hours later. Despite increased monocyte and granulocyte activation and increased levels of monocyte chemotactic protein-1, which upregulates monocyte tissue factor expression in vitro, monocyte tissue factor expression was not increased at the end of cardiopulmonary bypass. Furthermore, at this time the monocytes were less sensitive to in vitro stimulation by endotoxin. These results might be explained by simultaneous enhanced levels of interleukin-10, which effectively downregulates monocyte tissue factor expression in vitro. Twenty hours after cardiopulmonary bypass was discontinued, the tissue factor expression on freshly isolated monocytes and on monocytes stimulated by endotoxin was significantly increased compared with preoperative levels. At this time increased activation markers of granulocytes, monocytes, and lymphocytes were also recorded. None of the measured parameters was found to be different between the groups. CONCLUSIONS The tissue factor expression on circulating monocytes is upregulated the day after heart operations. The clinical relevance and the regulatory mechanism behind the enhanced expression, however, are not fully elucidated.

Complement activation during cardiopulmonary bypass: Effects of immobilized heparin

The role of complement in biocompatibility reactions and the correlation between complement activation during cardiopulmonary bypass (CPB) and postperfusion syndrome have inspired attempts to improve the biocompatibility of extracorporeal blood oxygenation devices. Here we assessed the effect of immobilized heparin on the generation of C3a and terminal complement complexes during CPB. Thirty patients undergoing aortocoronary bypass were randomized to CPB with either heparin-coated (Duraflo II; Bentley, Irvine, CA) or noncoated control membrane oxygenators (Univox; Bentley). A standard dose of heparin (300 IU/kg) was given to the control group while the heparin dose was reduced to 30% (100 IU/kg) in the heparin-coated group. Significantly lower levels of terminal complement complexes were detected in the heparin-coated group by the end of CPB. From 28 +/- 5 AU/mL (heparin-coated group) and 26 +/- 3 AU/mL (control group, mean +/- standard error of the mean) the terminal complement complex levels increased to 391 +/- 35 AU/mL and 602 +/- 47 AU/mL, respectively (p < 0.002). This difference was still apparent 180 minutes after CPB. Although there was no difference in C3a levels between the two groups at the end of CPB, C3a levels were significantly lower in the heparin-coated group 30 minutes after CPB (194 +/- 18 ng/mL and 307 +/- 18 ng/mL in heparin-coated and control groups, respectively; p < 0.001). We conclude that the heparin-coated surface is more biocompatible with regard to complement activation than is the ordinary unmodified surface in extracorporeal circuits.

Decreased Blood Loss After Cardiopulmonary Bypass using Heparin-Coated Circuit and 50% Reduction of Heparin Dose

In a randomized, double-blind study of patients undergoing elective coronary artery grafting, the effect of heparin-coated circuit combined with 50% reduction of systemic heparin bolus was investigated. Ten patients comprised group HC (heparin-coated) and ten group C (controls). The mean total doses of heparin were 172 IU/kg in group HC and 416 IU/kg in group C and the respective protamine doses were 0.96 and 3.96 mg/kg (both p < 0.001). Activated clotting times during cardiopulmonary bypass were significantly shorter in group HC, and both intra- and postoperative bleeding was significantly less than in group C (7.7 vs. 11.7 ml/kg, p = 0.036, and 6.9 vs. 9.7 ml/kg, p = 0.004). Hemoglobin loss via the drains was 22.5 g in group HC and 43.7 g in group C (p < 0.005). Hemolysis at the end of bypass was significantly greater in group C. Apart from one perioperative myocardial infarction in group HC the postoperative course was uneventful. Use of a heparin-coated circuit is concluded to permit complication-free reduction of heparin and protamine doses and to decrease both intra- and postoperative bleeding, which may favorably influence the outcome of coronary artery grafting.

Use of a Vital Capacity Maneuver to Prevent Atelectasis after Cardiopulmonary Bypass An Experimental Study

Background Respiratory failure secondary to cardiopulmonary bypass (CPB) remains a major complication after cardiac surgery. The authors previously found that the increase in intrapulmonary shunt was well correlated with the amount of atelectasis. They tested the hypothesis that post‐CPB atelectasis can be prevented by a vital capacity maneuver (VCM) performed before termination of the bypass. Methods Eighteen pigs received standard hypothermic CPB (no ventilation during bypass). The VCM was performed in two groups and consisted of inflating the lungs during 15 s to 40 cmH2 O at the end of the bypass. In one group, the inspired oxygen fraction (FIO2) was then increased to 1.0. In the second group, the FIO2 was left at 0.4. In the third group, no VCM was performed (control group). Ventilation‐perfusion distribution was measured with the inert gas technique and atelectasis by computed tomographic scanning. Results Intrapulmonary shunt increased after bypass in the control group (from 4.9 +/‐ 4% to 20.8 +/‐ 11.7%; P < 0.05) and was also increased in the vital capacity group ventilated with 100% oxygen (from 2.2 +/‐ 1.3% to 6.9 +/‐ 2.9%; P < 0.01) but was unaffected in the vital capacity group ventilated with 40% oxygen. The control pigs showed extensive atelectasis (21.3 +/‐ 15.8% of total lung area), which was significantly larger (P < 0.01) than the proportion of atelectasis found in the two vital capacity groups (5.7 +/‐ 5.7% for the vital capacity group ventilated with 100% oxygen and 2.3 +/‐ 2.1% for the vital capacity group ventilated with 40% oxygen. Conclusion In this pig model, postcardiopulmonary bypass atelectasis was effectively prevented by a VCM.

High incidence of Chlamydia pneumoniae in sclerotic heart valves of patients undergoing aortic valve replacement

Chlamydia pneumoniae has previously been demonstrated in the atherosclerotic lesions of various arteries, including the coronary arteries, and has been proposed to play a role in the pathogenesis of atherosclerosis. A prospective study of the incidence of C. pneumoniae in the sclerotic valves of patients undergoing aortic valve replacement because of aortic stenosis and in the aortic valves of cases dying of non-cardiac reasons and undergoing forensic autopsy was undertaken. The results were correlated to serological markers of past (IgG) or persistent (IgA) C. pneumoniae infection. C. pneumoniae, as determined by the polymerase chain reaction (PCR), was detected in the aortic valve in 19/39 (49%) patients and in 1/11 (9%) autopsy controls (p = 0.018) and confirmed by electron microscopy in one patient. There was no significant difference in the incidence rate of IgG or IgA antibody positivity between PCR-positive and PCR-negative cardiac patients. These results extend the hypothesis of a pathogenic role of C. pneumoniae in atherosclerosis to include also aortic valve sclerosis.

Heparin coating reduces blood cell adhesion to arterial filters during coronary bypass: a clinical study.

Deleterious effects of cardiopulmonary bypass (CPB) are partly sequelae of blood-foreign surface reactions. Coating the inner surfaces of CPB sets with heparin has been shown to decrease activation of humoral cascade systems. The aim of this study was to investigate whether the heparin-coated CPB sets influence adhesion of blood cells to surfaces of arterial filters during CPB. Thirty-one patients undergoing coronary artery bypass grafting were studied. In the control group (C) standard CPB sets and standard doses of heparin (300 IU/kg) were employed; in the HC (heparin-coated) group, heparin-coated CPB sets and reduced heparin doses (range, 150 to 225 IU/kg) were used. Two additional groups were also studied; group FC (coated filter), with standard CPB sets and heparin-coated arterial filters (heparin dose, 300 IU/kg), and group OC (uncoated filter), with heparin-coated CPB sets and standard arterial filters (heparin dose, 300 IU/kg). The inner surfaces of the arterial filters were examined after CPB with scanning electron microscopy. Scanning electron microscopy demonstrated almost clean surfaces in heparin-coated filters even when other parts of the circuit were uncoated. Using an arbitrary adhesion score, significant differences between the groups were noted in the adhesion grade; it was lowest in group HC (2.2 +/- 0.27 [mean +/- standard error of the mean]) versus group C (5.4 +/- 0.53; p < 0.001). In group FC it was marginally higher than in group HC but almost significantly lower than in group OC (2.6 +/- 0.68 versus 5.4 +/- 0.81; p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical evaluation of duraflo II heparin treated extracorporeal circulation circuits (2nd version): The European working group on heparin coated extracorporeal circulation circuits

OBJECTIVES To evaluate whether the application of heparin treated circuits for elective coronary artery surgery improves postoperative recovery, a European multicenter randomised clinical trial was carried out. METHODS In 11 European heart centers, 805 low-risk patients underwent cardiopulmonary bypass (CPB) with either an untreated circuit (n = 407) or an identical but heparin treated circuit (n = 398, Duraflo II). RESULTS Significant differences were found among participating centers with respect to patient characteristics, blood handling procedures and postoperative care. The use of heparin treated circuits revealed no overall changes in blood loss, blood use, time on ventilator, occurrence of adverse events, morbidity, mortality, and intensive care stay. These results did not change after adjustment for centers and (other) prognostic factors as analysed with logistic regression. In both groups no clinical or technical (patient or device related) side effects were reported. Because female gender and aortic cross clamp time appeared as prognostic factors in the logistic regression analysis, a subgroup analysis with these variables was performed. In a subpopulation of females (n = 99), those receiving heparin treated circuits needed less blood products, had a lower incidence of rhythm disturbances and were extubated earlier than controls. In another subgroup of patients with aortic cross clamp time exceeding 60 min (n = 197), the amount of patients requiring prolonged intensive care treatment (> 24 h) was significantly lower when they received heparin treated circuits versus controls. CONCLUSION These findings suggest that improved recovery can be expected with heparin treated circuits in specific higher risk patient populations (e.g. females) and when prolonged aortic cross clamp time is anticipated. Further investigations are recommended to analyses the clinical benefit of heparin treated circuits in studies with patients in different well defined risk categories and under better standardised circumstances.

Heparin-coated cardiopulmonary bypass circuits reduce blood cell trauma. Experiments in the pig

Blood cell trauma and postoperative bleeding remain important problems in cardiopulmonary bypass (CPB). We compared heparin-coated with non-coated circuits in the pig. Twenty animals were perfused for 2 h at normothermia using membrane oxygenators (Bentley Bos 50). Two groups were studied. In the non-coated group (NC, n = 11) the CPB circuits used were without a heparin coating. This group had systemic heparinization of 400 IU/kg to maintain an ACT (activated clotting time) of over 400 s during CPB. In the coated group (C, n = 9), all surfaces exposed to blood in the CPB circuits were heparin-coated. This group had the heparin dose reduced to 25% (100 IU/kg) without further administration regardless of ACT. During CPB, group C displayed shorter ACT (per definition), higher platelet count, platelet adhesion and lower fibrinolysis and haemolysis (P less than 0.05) as compared to group NC. No thromboembolic events were detected during CPB. Three animals in group NC and 4 animals in group C were weaned from CPB and protaminized. Four hours postoperatively, the leucocyte consumption was two-fold greater and blood loss about four-fold greater in group NC as compared with group C (P less than 0.05). Perfusion with heparin-coated surfaces reduces blood cell trauma. The decreased postoperative blood loss observed in group C is probably explained by the reduced dosages of heparin and protamine.