212 Rottembourg

CAPD Is More Advanfageous than Hemodialysis

Jacques 6. Rottembourg Groupe Hospitalier Pitie-Salpetriere, Paris, France

Cardiovascular events are the most frequent cause of death in patients with end-stage renal disease (1). The long-term prognosis of hemodialysis as well as of peritoneal dialysis patients (mainly continuous ambulatory peritoneal dialysis (CAPD) patients) is dependent on their cardiovascular status.

Are patients with an unstable cardiovascular sys- tem more appropriate candidates for peritoneal di- alysis? There is as yet no definitive answer to this dificult question. Although there are some obser- vations on the treatment of congestive heart failure by peritoneal dialysis (2-4), the best way to answer the question is to investigate the cardiovascular sta- tus of CAPD patients and to determine if the hemo- dynamic changes observed during CAPD are favor- able for those with an unstable cardiovascular sys- tem.

Cardiovascular System in Uremic Patients and Effects of Hemodialysis

Cardiovascular diseases have an adverse prognosis among uremic patients resulting in heart failure, myocardial infarction, and death (5-6). Predisposing risk factors for congestive heart failure were assessed in different heart diseases: hypertrophic hyperkinetic cardiomyopathy, dilated cardiomyopathy, and is- chemic heart disease. The best predictors for hyper- trophic hyperkinetic disease were diastolic hyperten- sion and hyperparathyroidism (7). The prevalence of hyperparathyroidism is significantly higher in he- modialysis patients with congestive cardiomyopathy (8). The concept of a specific cardiomyopathy asso- ciated with uremia is still debated (9).

It is generally agreed that hemodialysis produces an improvement in left ventricular (LV) systolic function (10): an increase in LV contractility and a decrease in left ventricular end-diastolic volume and stroke volume. However, the improvement in LV systolic function depends on predialysis LV volume and systolic function; hemodialysis induces an in- crease in LV ejection fraction in patients with a reduced ejection fraction prior to dialysis but not in those with a normal predialysis ejection fraction (1 1). The loss in body weight during the hemodialysis

Address correspondence to: Jacques B. Rottembourg, MD, Groupe Hospitalier Pitie-Salpetriere, 47-83 Boulevard de I'H6pital. 75651 Paris Cedex 13, France. Seminurs in Dialysis-Vol 5, No 3 (July-Sept) 1992 pp 212- 214

session is only partially responsible for the improved LV performance and suggests that other factors may also account for the improvement, such as an in- crease in calcium concentration, correction of aci- demia, and afterload reduction resulting from de- creased blood pressure.

Compared to hemodialysis, CAPD theoretically possesses several hemodynamic advantages: CAPD is continuous and exerts little acute effect on intra- vascular volume; the dialysate base (lactate) has no hemodynamic effects; electrolyte shifts are minimal; blood hemoglobin levels appear to be generally higher; and the hemodynamic effects of a fistula are eliminated. On the other hand, hyperlipidemia due to continuous glucose supply and hyperinsulinemia may increase the risk of atherosclerosis. These factors impact on cardiac structure and function, the control of hypertension, and the effects of increased abdom- inal pressure, all of which relate closely to the ques- tion of whether cardiovascular status is more pro- tected during CAPD than during hemodialysis.

Effects of CAPD on Cardiac Structure and Function

Echocardiographic findings in CAPD patients have been described by many authors ( 12- 16). Most of them compared CAPD patients either with healthy control subjects or with hemodialysis pa- tients; there are few longitudinal studies exclusively in CAPD patients. Most patients had a history of hypertension before beginning CAPD. During CAPD blood pressure was well controlled, but half the patients were maintained on anti-hypertensive drugs.

LV hypertrophy, either concentric or asymmetric, was present in 65% of the patients, asymmetric septa1 hypertrophy in 50%, left atrial dilatation in 49%, pericardial thickening in 4576, and LV dilatation in 25%. The increase in LV muscle mass was mainly due to the thickening of the interventricular septum. The muscle mass index correlated directly with the cardiac index and the creatinine concentration and was inversely correlated with the hemoglobin con- centration (12). The left atrial diameter index was inversely correlated with the LV ejection fraction, the fractional shortening, and the heart rate and directly correlated with the LV muscle mass index.

In the studies published by Wizeman (12) and in the one by Hiiting (16) the mean LV ejection fraction was 62 k 13%, in the normal range, in 12% and

WHICH DlALVTlC THERAPV IS BEST? 213

15% of the patients, respectively, the LV ejection fraction was less than 45%. Both fractional shorten- ing and velocity of circumferential fiber shortening indicated normal or hyperdynamic LV systolic func- tion. Both stroke volume index (64 k 16 ml/m2) and cardiac index (4.8 2 1.6 ml/m2.min) suggested a hyperdynamic circulatory state as compared to con- trol subjects. Using pulsed Doppler echocardiogra- phy Wizeman ( 12) and Hiiting (1 6) found that peak and mean velocities of atrial filling waves were greater and the ratio of early to late atrial filling velocities were smaller, indicating diastolic dysfunc- tion in CAPD patients compared to normal subjects.

Hemodynamic values in CAPD patients are simi- lar to those observed in hemodialysis patients follow- ing the sessions, with the exception of cardiac index and heart rate. During CAPD, LV systolic function shows a trend toward normalization of heart param- eters. The cardiac index is lower in patients on CAPD than in posthernodialysis patients, due to a lower heart rate. This lower heart rate probably results from the consistently euvolemic state associated with CAPD. Comparing hemodialysis and CAPD pa- tients, Alpert (17) had similar findings, showing a higher mean velocity of circumferential fiber short- ening during CAPD. In CAPD patients on a 2-year follow-up, LV function does not deteriorate (1 8). Despite the reduction of mean blood pressure, LV mass, LV end-diastolic volume, and ejection fraction remain unchanged. The cardiovascular functional status of CAPD patients does not change over time ( 19).

Coronary Artery Diseases in CAPD Patients

Coronary artery disease (CAD), a frequent finding in patients with end-stage renal disease, is often associated with hypertension and present before starting renal replacement therapy. The prevalence of CAD is probably of the same magnitude in CAPD as in HD patients, although studies of prevalence are lacking. Theoretically, CAPD might have some ad- vantages over HD in the treatment of patients with significant CAD. First, CAPD is associated with a steady state of fluid regulation which facilitates drug therapy such as nitrates, calcium channel blockers, or P-adrenergic blockers. Second, arterial hyperten- sion can be better controlled, which may benefit myocardial oxygen demand as well as the progres- sion of CAD (17). A similar effect can be expected by the absence of an arteriovenous fistula, which can increase cardiac output and myocardial oxygen de- mand. Third, CAPD is associated, on a long-term basis, with a reduction of internal LV dimensions, a situation that is comparable only with the postdi- alysis state in hemodialysis (20).

Control of Hypertension

Hypertension is common in patients with end- stage renal disease affecting 80% of the patients entering dialysis. In the general population several

studies have indicated that high blood pressure is a leading factor predisposing to stroke and heart fail- ure. A reduction of blood pressure by drugs and/or dialysis will prolong life and reduce the occurrence of stroke and congestive heart failure.

CAPD seems to offer a more rapid and effective control of blood pressure (2 1-24) than hemodialysis. Following the initiation of CAPD therapy in hyper- tensive patients, early and sustained decreases in systolic and diastolic blood pressure are seen; 17% of these patients no longer require medication at 1 month, and 30% are drug free at 1 year. Of those who are still using medications there is a tendency to decrease the number of drugs used per day. Never- theless, 25% of the patients treated by CAPD still have uncontrolled hypertension. Hamburger et al. (21) have suggested that CAPD is superior to he- modialysis in the treatment of patients with dialysis refractory hypertension and its cardiovascular com- plications. This hypothesis requires a long-term mul- ticenter study.

Various Effects of CAPD

Multiple factors may influence cardiac perform- ance following intraperitoneal fluid infusion: de- creased venous return due to inferior vena cava compression or, perhaps, increased intrathoracic pressure; direct cardiac compression by the dia- phragm and increased SVR due to decreased cardiac output (25). Most studies of CAPD patients do not show any impairment in cardiac performance with 2-liter infusion volumes (26). Impairment of LV systolic function may, however, occur in CAPD patients with increased LV wall thickness who use 3-liter infusion volumes. Decreased LV compliance in this group of patients makes them particularly vulnerable to decreased LV preload resulting from a reduction of venous return. In addition, impaired LV filling from the altered diastolic mechanical properties may contribute to orthostatic hypotension (27).

Autonomic control of the cardiovascular system is modified to a comparable degree in hemodialyzed and CAPD patients (28). Studies of Holter monitor- ing in CAPD patients show a frequent occurrence of atrial and ventricular premature beats (29). How- ever, there are no differences in the type and fre- quency of premature beats between the recordings performed on a dialysis day or on a day on which dialysis is deliberately withheld. Compared to he- modialysis patients, the recordings are less altered in CAPD patients (29). Thus CAPD seems to be a safe modality that is often preferable to hemodialysis in older patients with unstable cardiac disease.

Conclusions

Structural changes in the hearts of patients with end-stage renal disease are independant of the tech- nique of renal replacement therapy. Thus the spec- trum of potential cardiac complications such as atrial

214 Rottembourg

fibrillation, sudden death, cardiac failure, myocar- dial infarction, and severe ventricular arrhythmias appears qualitatively comparable in patients treated by either hemodialysis or CAPD. Long-term prog- nosis depends on the cardiac status at the time dialysis is initiated as well as the effects of dialytic therapy (27). However, in the short term, CAPD is associated with a more favorable cardiac hemody- namic state than HD: lower mean blood pressure, lower LV end-diastolic volume, lower LV hypertro- phy, and higher LV mean velocity of circumferential fiber shortening. Hemodynamically, CAPD is com- parable to HD only during the period immediately following hemodialysis.

In CAPD the character of the continuous manage- ment of fluid and electrolyte balance may create a more favorable setting for cardiac stability than he- modialysis. In patients with hypertrophied left ven- tricles with reduced diastolic compliance, a reduction of cardiac preload (as induced by rapid ultrafiltra- tion) may impair LV filling and be associated with a high incidence of sudden death. Acute correction of electrolyte disturbances by hemodialysis may impair diastolic compliance. Intermittent overhydratation in hemodialysis patients may dispose to pulmonary congestion in patients with hyperdynamic hyper- trophic hearts and may impair myocardial perfusion in CAD. The effects of cardiovascular drug therapy may be unpredictable in HD patients in the absence of equilibrium in fluid status.

In contrast, CAPD does not show any benefit in protecting against autonomic neuropathy or in im- paired parasympathetic control of heart. Standard 2- liter dialysis infusion does not appear to impair cardiac performance. Thus, in the management of patients with end-stage renal diseases, it is probably more important how a method is applied and how much experience with a method has been accumu- lated. Nevertheless, in some situations CAPD could benefit patients with unstable cardiac diseases.

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