SYMPTOMATIC ATRIAL ARRHYTHMIAS IN HEMODIALYSIS PATIENTS

Abstract

Background/Aims: Cardiac arrhythmias are frequent in hemodialysis patients and can interrupt treatment. However, the frequency and risk factors have remained unclear because previous reports of arrhythmias in dialysis patients have usually been continuous-monitoring studies that looked at all cardiac ectopy regardless of its seriousness. Methods: We reviewed retrospectively only symptomatic atrial arrhythmias in a population of 106 maintenance hemodialysis patients over three years, in order to estimate their actual frequency and any risk factors. Results: Ten patients, seven men and three women, required treatment for atrial arrhythmias (9.4%): four for supraventricular tachycardia, three for atrial flutter, and three for atrial fibrillation. Their mean age was 53.7 ± 6.1 years; five of them were ≤40 years. Seven arrhythmias were new, three were recurrences. All but one occurred between 3 and 4 hours of hemodialysis, and dialysis had to be stopped in nine instances. There was no pattern of hypotensive episodes preceding the arrhythmias. Mean serum K⁺ drawn at the time of the arrhythmias was 3.8 ± 0.2 mEq/L. Mean plasma intact parathormone was 1128 ± 417 pg/mL, compared to 454 ± 58 pg/mL for our entire hemodialysis population (p = .0036). Subsequent echocardiograms showed abnormalities in 9/10 patients: five had left ventricular hypertrophy, six had left atrial enlargement, five had valvular lesions (four mitral regurgitation; one aortic incompetence), and three had ejection fractions <50%. There were four deaths in these patients over the next 14 months, but probably only one was cardiac. Conclusions: Serious atrial arrhythmias are common in a hemodialysis population. Risk factors for symptomatic atrial arrhythmias in hemodialysis patients may include hyperparathyroidism and echocardiographic findings of chamber enlargement, valvular lesions, or ventricular dysfunction.

• Hemodialysis
• Atrial arrhythmias
• Hyperparathyroidism
• Echo-cardiography

INTRODUCTION

Cardiac arrhythmias are frequent in hemodialysis patients. The prevalence of both atrial and ventricular arrhythmias has been reported to vary from 17–76% of the total hemodialysis population [1-2]. Various pathogenetic factors, including electrolyte and acid-base disturbances, chronic hypertension, cardiomyopathy, and preexisting coronary artery disease with low ejection fraction have been investigated as possible causes for this observation [[3]], but conclusive data about the role of each of these are still lacking. Many of the studies of atrial arrhythmias in hemodialysis patients have involved Holter monitoring, which records all ectopic activity, serious or not [4-9]. Such studies have suggested that as many as 50% of all hemodialysis patients have atrial extrasystoles [[10]]. In practice, however, far fewer than half our hemodialysis patients require treatment for atrial arrhythmias. The purpose of this study was to estimate the incidence of symptomatic atrial arrhythmias in a population of hemodialysis patients, and to identify any risk factors associated with these arrhythmias.

Methods

We retrospectively reviewed the records of the 106 maintenance hemodialysis patients at Nassau County Medical Center, a public teaching hospital in suburban New York, during the preceding three years. Three atrial arrhythmias were considered as requiring treatment: supraventricular tachycardia (SVT), atrial flutter (AFL), and atrial fibrillation (AFI). In addition, we noted the patients' age, sex, underlying conditions, medications (both cardiac and noncardiac), and any temporal relationship of the arrhythmia to dialysis, including whether a treatment had to be terminated early. We also looked at the patients' intact parathormone levels (when available), hematocrits, and whether they had internal jugular or subclavian venous catheters. Any subsequent need for hospitalization and/or long term antiarrhythmic treatment was recorded, as were the findings on echocardiography. Group data are presented as mean ± standard error of the mean. Student's t-test for unpaired data was used to determine statistical differences.

RESULTS

In all, 10 of the 106 patients, seven men and three women, required treatment for atrial arrhythmias (9.4%). The mean age of these patients was 53.7 ± 6.1 years; five of them were ≤40 years. Seven of the arrhythmias were new onset (4 SVT, 2 AFL, and 1 AFI), and three were recurrences or exacerbations of previous arrhythmias (1 AFL, 2 AFI). All these arrhythmias, both new and old, except for 1 AFI, occurred between 3 and 4 hours of hemodialysis. There was no pattern of hypotensive episodes preceding the arrhythmias. Mean serum [K⁺] drawn at the time of the arrhythmias was 3.8 ± 0.2 mEq/L. The average hematocrit was 31 ± 1.3%. Mean plasma intact parathormone was 1128 ± 417 pg/mL compared to an average of 454 ± 58 pg/mL for our hemodialysis population (p = .0036). None of the patients had a neck venous catheter at the time of the arrhythmia.

Five of the 10 patients required hospitalization; four were already in hospital (for noncardiac conditions) when the arrhythmia occurred, and one refused admission. Dialysis had to be stopped for all four patients with SVT and 2 with preexisting AFI who developed a rapid ventricular response (Tab. 1).

Table 1. Symptomatic Atrial Arrhythmias in Hemodialysis Patients

Arrhythmia	Number of Patients	Hospitalized	Dialysis Terminated
Supraventricular tachycardia (SVT)	4	3	4
Atrial flutter (AFL)	3	2	3
Atrial fibrillation (AFI)	3	3	2

All 10 patients subsequently had echocardiograms. Table 2 shows the results of echocardiography following control of the arrhythmias. Patients with AFL tended to have a lower ejection fraction than those with SVT. Half the patients had left ventricular hypertrophy, and six of the 10 had left atrial enlargement. Three of the four patients with SVT were successfully treated with adenosine; the fourth refused treatment. The AFL responded to diltiazem or adenosine, and the AFI patients' ventricular rates were controlled with digoxin. Five of the patients were found to have coexisting valvular lesions on echocardiography (four had mitral regurgitation; one had aortic incompetence). Three patients had ejection fractions <50% (range 30–40%).

Table 2. Echocardiographic Findings in Hemodialysis Patients with Symptomatic Atrial Arrhythmias

Arrhythmia	Mean Ejection Fraction	Left Ventricular Hypertrophy	Left Atrial Enlargement
SVT (4)	50 ± 7%	3/4	3/4
AFL (3)	37 ± 12%	1/3	2/3
AFI (3)	Not estimated	1/3	1/3

During the 14 months following the end of the study, four of the 10 patients died. The patient with the normal echocardiogram, an 85-year-old man, died suddenly at home within a few weeks of beginning dialysis. The other three deaths were due to infection, intracranial hemorrhage, and calciphylaxis.

DISCUSSION

Most prior studies of cardiac arrhythmias in hemodialysis patients [4-11] have focused on asymptomatic arrhythmias, using either 24–hour Holter monitoring or intradialytic 12–lead ECGs. Most of the abnormal atrial beats recorded in such reports would never come to the attention of the clinician. In the present study we focused on only those atrial arrhythmias that actually required treatment. Our findings are consistent with some, but not all, earlier results.

No specific risk factor has been conclusively linked to atrial arrhythmia; suggested risk factors have included old age, male sex, diabetes mellitus, hyperparathyroidism, changing dialysate potassium concentration, and decreased erythrocyte K⁺ content [[11]]. Seven of our 10 patients were men; serious atrial arrhythmias may indeed be more frequent in male patients. However, age was not an apparent risk in our population, as half our patients were ≤40 years old. All but one arrhythmia in our patients occurred toward the end of a dialysis treatment, suggesting that electrolyte flux might be a factor. This is consistent with the findings of a previous study [[11]]. Mean serum K⁺ at the time of the arrhythmia was within the normal range; however, extracellular [K⁺] looks at only a tiny fraction of total body K⁺ and tells nothing about transcellular flux of the ion.

One striking result was that the mean serum parathormone level in our atrial arrhythmia patients was more than double that of our hemodialysis population. Naso et al. [[12]] concluded that the seriousness of arrhythmias during dialysis is independent of the presence of cardiomyopathy, but found higher parathormone levels in the patients with arrhythmias. Our patients' hyperparathyroidism is consistent with the latter result, but nearly all of them had abnormalities on echocardiography as well. These findings may well be related, since hyperparathyroidism has been suggested to have an adverse effect on myocardial function in dialysis patients. Drueke et al. [[13]] reported improvement in cardiac function in dialysis patients following parathyroidectomy, and Coratelli et al. [[14]] found that administration of 25–OH D₃ to dialysis patients led to a fall in serum parathormone levels and improvement in echocardiographic findings.

Although none of our 10 patients had a debilitating cardiomyopathy, nine of them had abnormal echocardiograms (Tab. 2). Half had left ventricular hypertrophy; half had mitral or aortic valvular disease, and 60% had atrial enlargement. Only two out of 10 patients had no anatomic changes on echocardiography, and one of these had a low ejection fraction (30%). One previous study was unable to document a difference in echocardiographic findings between groups of dialysis patients with and without arrhythmias [[15]]. Ironically, the one probable cardiac death in our patients was in the one with the normal echocardiogram, possibly due to ischemia.

In conclusion, in our experience, symptomatic atrial arrhythmias are common in hemodialysis patients (slightly under 10%) but less frequent than predicted by 24–hour monitoring studies. Atrial arrhythmias may be as frequent among hemodialysis patients ≤40 years of age as among older patients. These arrhythmias are independent of episodes of hypotension during dialysis but usually arise, or are exacerbated, during the last hours of dialysis, often necessitating cessation of the treatment. Patients with very high serum intact parathormone levels and those with valvular disease, low ejection fraction, left ventricular hypertrophy, or left atrial enlargement on echocardiography appear to be at risk for developing intradialytic atrial arrhythmias.

ACKNOWLEDGMENT

An earlier version of this study was presented at the annual meeting of the American Society of Nephrology, San Antonio, Texas, November 4, 1997.