Assessment of changes in general health status using the short-form 36 questionnaire 1 year following coronary artery bypass grafting.

OBJECTIVE: The problem addressed in the study was to gain a greater understanding of the health benefits of coronary artery bypass grafting (CABG). The purpose of the study was to assess general health status, using the short-form (SF)-36 questionnaire, approximately 12 months following CABG, and to document any associations between pre-operative health status, level of social support, coronary artery disease (CAD) risk factors, CAD symptom severity and post-operative health status. METHODS: The study was prospective and observational in design and included assessments at two time points, namely pre-operatively in a hospital outpatient department (1995-1996) and post-operatively at home (1996-1997). Two hundred and fourteen patients awaiting elective CABG were recruited a month before the expected date of operation. Pre-operative assessment included: (1), severity of symptoms; (2), CAD risk factors; (3), SF-36 questionnaire; and (4), social activities questionnaire. Post-operative assessment measured health status using the SF-36 instrument (mean, 16.4 months). Correlation and multiple linear regression analyses were used to identify factors associated with improved health status following CABG. RESULTS: Two hundred and fourteen patients were assessed pre-operatively and underwent CABG. There was a 4.8% 30-day mortality rate, and 183 patients were followed for a mean of 16.4 months after CABG. SF-36 scores following CABG were improved across all of the eight domains (P<0.001). A higher social network score and higher pre-operative health status were associated with improved health status. Patients with lower health levels (SF-36 scores) prior to CABG were less likely to gain improvement in health (SF-36 scores) following CABG. Lower SF-36 scores following operation were influenced by the presence of diabetes mellitus, cigarette smoking, younger age, a high socio-economic deprivation category and higher alcohol intake. Many patients had uncorrected CAD risk factors at pre-operative assessment. CONCLUSIONS: The SF-36 instrument was shown to be a useful and sensitive tool to assess differences and changes in the general health status of patients before and following CABG. High levels of social support were associated with improved health status post-operatively. Lower pre-operative general health status, the presence of diabetes mellitus and cigarette smoking were associated with poorer post-operative general health status.

In vitro function and durability assessment of a novel polyurethane heart valve prosthesis.

While flexible-leaflet, central-flow prosthetic heart valves promise relief from anticoagulation therapy, they continue to be restricted by inadequate durability. In consequence, a novel trileaflet valve, made entirely from polyurethane, has been developed. A batch of 6 consecutively manufactured polyurethane valves was subjected to hydrodynamic function and accelerated fatigue testing. Computerized data acquisition and control systems have been introduced to improve valve testing methodologies. In terms of hydrodynamic function, the polyurethane valve demonstrates transvalvular pressure gradients similar to those for a bioprosthetic valve (Carpentier-Edwards) and levels of retrograde flow significantly less than those for either the bioprosthetic valve or a bileaflet mechanical valve (St Jude Medical). The equivalent of 10 years of cycling without failure has been exceeded by all 6 polyurethane valves in accelerated fatigue tests with 2 valves remaining intact after 674 million cycles (equivalent to approximately 17 years) in continuing tests. Highspeed photography revealed considerable differences in leaflet motion between valves cycled at accelerated and physiological rates.

Resting and total energy expenditure in patients with ischemic heart disease.

Total energy expenditure (TEE) was measured by doubly labeled water in 13 preoperative patients undergoing elective coronary artery surgery and compared to resting energy expenditure (REE) measured by indirect calorimetry (IC) calculated from the Harris-Benedict (HB) formula or from formulas based on midarm circumference and arm muscle circumference. Mean REE measured by IC and calculated from the HB, midarm circumference, arm muscle circumference formulas were 62, 75, 62, and 69%, respectively, of TEE measured by doubly labeled water. REE measured by IC correlated significantly with that predicted by the HB (p = 0.006) but not the anthropometric formulas. The relationship between REE derived from anthropometric predictive formulas and REE measured by IC is altered in ischemic heart disease.

Effects of cardiac surgery and intraoperative hypothermia on energy expenditure as measured by doubly labelled water.

Total energy expenditure (TEE) was measured over two 10-day periods, before and after operation in 16 patients undergoing coronary artery surgery and randomized to have cardiopulmonary bypass with an intraoperative blood temperature of either 28 or 20 degrees C. TEE was measured with doubly labelled water containing stable isotopes of hydrogen and oxygen to allow calculation of TEE over fixed periods from the differential rate of excretion of the two isotopes. Results were available for eight patients in the 28 degrees C group but for only seven in the 20 degrees C group (one patient in this group was excluded as the temperature allocated was not achieved). The groups were similar with respect to body-weight and lean body mass. The 20 degrees C group received more grafts than the 28 degrees C group, resulting in an increase in cross-clamp and bypass times. Mean preoperative TEE was similar in both groups. The mean difference in fractional turnover rates of hydrogen and oxygen was not significantly different in the postoperative period. There was a non-significant increase in the mean 10-day postoperative TEE, calculated in total calories, of 4.7 per cent in the 28 degrees C and 5.1 per cent in the 20 degrees C group. When changes in postoperative TEE were calculated according to lean body mass, the mean increases were respectively 3.7 and 3.2 per cent. Cardiac surgery utilizing cardiopulmonary bypass and intraoperative hypothermia results in only a modest increase in postoperative TEE. In this study a more profound level of intraoperative hypothermia did not influence the change in postoperative TEE.

Assessment of coronary artery bypass graft flow by intraoperative Doppler ultrasound technique.

A high frequency (10 MHz) Doppler ultrasound pencil probe was used to estimate flow in coronary artery bypass grafts in vitro and during cardiac surgery. In vitro, increasing the angle of the Doppler transducer in relation to flow caused underestimation of the Doppler derived flow, and using the external rather than internal vessel diameter to calculate cross sectional area caused significant overestimation. This overestimation was considerably greater for the internal mammary artery. Accurate flow estimation was obtained in vitro by the Doppler technique, but considerable variation occurred in patients studied during coronary artery bypass surgery. In conclusion, intraoperative Doppler ultrasound provides a qualitative assessment of phasic flow in coronary artery bypass grafts but is less accurate in quantifying absolute flow in these patients.

Non-invasive assessment by Doppler ultrasound of 155 patients with bioprosthetic valves: a comparison of the Wessex porcine, low profile Ionescu-Shiley, and Hancock pericardial bioprostheses.

One hundred and fifty five patients with 167 bioprosthetic valves (68 Wessex porcine, 54 Hancock pericardial, and 45 low profile Ionescu-Shiley pericardial valves) were studied by Doppler ultrasound. Valve gradients were calculated from the mitral and aortic flow velocities by the modified Bernoulli equation. Mean mitral gradients were significantly smaller across the Ionescu-Shiley valves than across the Wessex porcine or Hancock pericardial valves. Mitral pressure half time was, however, significantly longer in the Hancock pericardial than in the Wessex porcine or Ionescu-Shiley valves. No significant differences were seen among the groups of aortic bioprostheses, though the comparable size of Wessex porcine valves showed significantly higher gradients. Bioprosthetic regurgitation was detected in 13 of 103 mitral and 11 of 59 aortic valves, though it was suspected clinically in only 12 mitral and six aortic bioprostheses. Doppler ultrasound is a repeatable non-invasive method of acquiring haemodynamic information in vivo from a variety of bioprostheses and it can detect bioprosthetic regurgitation at an early stage.