Effects On The Cardiovascular System

In subsamples of the SOS study, cardiac function was examined at baseline and after 1 to 4 years of follow-up.

At baseline a surgically treated group (n = 41) and an obese control group (n = 31) were compared with a lean refrence group (n = 43) (25,26). As compared to lean subjects, the systolic and diastolic blood pressure, left ventricular mass and relative wall thickness were increased in the obese while the left ventricular ejection fraction (systolic function) and the E/A ratio (diastolic function) were decreased at baseline. After 1 year, all these variables had improved in the surgically treated group but not in the obese control group. When pooling the two obese groups and plotting left ventricular mass or E/A ratio as a function of quintiles of weight change, a 'dose' dependency was revealed, i.e. the larger the weight reduction, the larger the reduction in left ventricular mass (Figure 35.10) and the more pronounced the improvement in diastolic function (Figure 35.11). Unchanged weight was in fact associated with a measurable deterioration in diastolic function over 1 year.

In other small subgroups from SOS, heart rate variability from 24-hour Holter ECG recordings and 24-hour catecholamine secretion were examined (27). As compared to lean subjects, our examinations indicated an increased sympathetic activity and a withdrawal of vagal activity at baseline. Both these disturbances were normalized in the surgically treated group but not in the obese control group after 1 year of treatment.

Furthermore, questionnaire data from 1210 surgically treated patients and 1099 obese SOS controls examined at baseline and after 2 years were analysed with respect to various cardiovascular symptoms (5). At baseline the two groups were comparable in most respects. After 2 years, dyspnoea and chest discomfort were reduced in a much larger fraction of surgically treated as compared to controls. For instance, 87% of the surgically treated reported baseline dyspnoea when climbing two flights of stairs while only 19% experienced such

Figure 35.10 Changes in left ventricular mass (LVM) as a function of 1-year weight change quintiles (kg) in the SOS intervention study. Mean + SEM. Pooled echocardiography data of 38 surgically treated patients and 25 obese controls. Correlation for trend based on individual observations (n = 63). From Karason et al. (25), with permission

Figure 35.10 Changes in left ventricular mass (LVM) as a function of 1-year weight change quintiles (kg) in the SOS intervention study. Mean + SEM. Pooled echocardiography data of 38 surgically treated patients and 25 obese controls. Correlation for trend based on individual observations (n = 63). From Karason et al. (25), with permission

Figure 35.11 Changes in diastolic function, as indicated by the E/A ratio, in relation to 1-year weight change quintiles (kg) in the SOS intervention study. Mean + SEM. Pooled transmitral Doppler data of 41 surgically treated patients and 30 obese controls. Correlation for trend based on individual observations (n = 71). From Karason et al. (26), with permission

Figure 35.11 Changes in diastolic function, as indicated by the E/A ratio, in relation to 1-year weight change quintiles (kg) in the SOS intervention study. Mean + SEM. Pooled transmitral Doppler data of 41 surgically treated patients and 30 obese controls. Correlation for trend based on individual observations (n = 71). From Karason et al. (26), with permission dyspnoea at the 2-year follow-up. In the obese control group the corresponding figures were 69 and 57%, respectively (P < 0.001 for difference in change between groups).

Similarly, a high likelihood for sleep apnoea was observed in 23% of the surgically treated patients at baseline but only in 8% after 2 years of treatment. In the control group the corresponding figures were 22 and 20%, respectively (P < 0.001).

Figure 35.12 Annual progression rate of intima-media thickness in the carotid artery bulb in surgically treated obese patients (n = 14), obese controls (n = 9) and lean controls (n = 27) matched for gender, age and height. Mean + SEM. Progression rate measured ultrasonographically over 4 years in the two obese groups and over 3 years in the lean reference group. The weight change was — 22 + 10 kg in the operated group and 0 + 13 kg in the obese control group. From Karason et al. (28), with permission

Figure 35.12 Annual progression rate of intima-media thickness in the carotid artery bulb in surgically treated obese patients (n = 14), obese controls (n = 9) and lean controls (n = 27) matched for gender, age and height. Mean + SEM. Progression rate measured ultrasonographically over 4 years in the two obese groups and over 3 years in the lean reference group. The weight change was — 22 + 10 kg in the operated group and 0 + 13 kg in the obese control group. From Karason et al. (28), with permission

Physical inactivity was observed in 46% of the surgically treated group before weight reduction but only in 17% after 2 years. Corresponding figures in the obese control group were 33 and 29%, respectively (P < 0.001) (5). Thus physical inactivity not only contributes to the development of obesity but obesity prevents physical activity. This vicious circle is broken by surgical treatment.

Finally, the intima-media thickness of the carotid bulb was examined by means of ultrasonography at baseline and after 4 years in the SOS intervention study (28). A randomly selected lean reference group matched for gender, age and height was examined at baseline and after 3 years. As shown in Figure 35.12 the annual progression rate was almost three times higher in the obese control group (n = 9) as compared to lean reference subjects (P < 0.05). In the surgically treated group, the progression rate was normalized. Although resuls from this small study group need to be confirmed in larger trials, this study nevertheless offers the first data on hard endpoints after intentional weight loss.

We have also shown that the pulse pressure increases more slowly in the surgically treated group than in the obese control group after a mean follow-up of 5.5 years (19). In gastric bypass individuals the pulse pressure is in fact decreasing. These observa tions are of interest since it has been shown that, at a given systolic blood pressure, a high pulse pressure is associated with increased artrial stiffness (29), increased intima-media thickness (30) and increased cardiovascular mortality (31). Thus pulse pressure changes (19) as well as ultrasonographic measurements (28) indicate that surgical treatment is slowing down the increased atherosclerotic process in the obese.

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