Painless myocardial ischemia in chronic hemodialysed patients: a real event?

Monitoring blood potassium concentration in hemodialysis patients by quantifying T-wave morphology dynamics

We investigated the ability of time-warping-based ECG-derived markers of T-wave morphology changes in time ([Formula: see text]) and amplitude ([Formula: see text]), as well as their non-linear components ([Formula: see text] and [Formula: see text]), and the heart rate corrected counterpart ([Formula: see text]), to monitor potassium concentration ([Formula: see text]) changes ([Formula: see text]) in end-stage renal disease (ESRD) patients undergoing hemodialysis (HD). We compared the performance of the proposed time-warping markers, together with other previously proposed [Formula: see text] markers, such as T-wave width ([Formula: see text]) and T-wave slope-to-amplitude ratio ([Formula: see text]), when computed from standard ECG leads as well as from principal component analysis (PCA)-based leads. 48-hour ECG recordings and a set of hourly-collected blood samples from 29 ESRD-HD patients were acquired. Values of [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] were calculated by comparing the morphology of the mean warped T-waves (MWTWs) derived at each hour along the HD with that from a reference MWTW, measured at the end of the HD. From the same MWTWs [Formula: see text] and [Formula: see text] were also extracted. Similarly, [Formula: see text] was calculated as the difference between the [Formula: see text] values at each hour and the [Formula: see text] reference level at the end of the HD session. We found that [Formula: see text] and [Formula: see text] showed higher correlation coefficients with [Formula: see text] than [Formula: see text]-Spearman's ([Formula: see text]) and Pearson's (r)-and [Formula: see text]-Spearman's ([Formula: see text])-in both SL and PCA approaches being the intra-patient median [Formula: see text] and [Formula: see text] in SL and [Formula: see text] and [Formula: see text] in PCA respectively. Our findings would point at [Formula: see text] and [Formula: see text] as the most suitable surrogate of [Formula: see text], suggesting that they could be potentially useful for non-invasive monitoring of ESRD-HD patients in hospital, as well as in ambulatory settings. Therefore, the tracking of T-wave morphology variations by means of time-warping analysis could improve continuous and remote [Formula: see text] monitoring of ESRD-HD patients and flagging risk of [Formula: see text]-related cardiovascular events.

Cardiovascular impact in patients undergoing maintenance hemodialysis: Clinical management considerations

Patients undergoing maintenance hemodialysis develop both structural and functional cardiovascular abnormalities. Despite improvement of dialysis technology, cardiovascular mortality of this population remains high. The pathophysiological mechanisms of these changes are complex and not well understood. It has been postulated that several non-traditional, uremic-related risk factors, especially the long-term uremic state, which may affect the cardiovascular system. There are many cardiovascular changes that occur in chronic kidney disease including left ventricular hypertrophy, myocardial fibrosis, microvascular disease, accelerated atherosclerosis and arteriosclerosis. These structural and functional changes in patients receiving chronic dialysis make them more susceptible to myocardial ischemia. Hemodialysis itself may adversely affect the cardiovascular system due to non-physiologic fluid removal, leading to hemodynamic instability and initiation of systemic inflammation. In the past decade there has been growing awareness that pathophysiological mechanisms cause cardiovascular dysfunction in patients on chronic dialysis, and there are now pharmacological and non-pharmacological therapies that may improve the poor quality of life and high mortality rate that these patients experience.

Prevalence and Predictors of Arrhythmia in End Stage Renal Disease Patients on Hemodialysis

BACKGROUND

Sudden death is common in end-stage renal disease (ESRD). Cardiac arrhythmia is observed frequently in patients with ESRD and is thought to be responsible for this high rate of sudden death. This study investigated the prevalence and the predictors of arrhythmia in patients on maintenance dialysis.

METHODS

Ninety-four patients on hemodialysis program were enrolled in the study. Routine laboratory results were noted. Arrhythmia, periods of silent ischemia, and heart-rate variability analyses were obtained from 24-hour Holter monitor recordings. Corrected QT (QTc) dispersion was calculated from 12-lead surface EKG. Echocardiographic and tissue Doppler examinations were performed on interdialytic days as well. Ventricular arrhythmia was classified according to Lown classification; classes 3 and above were accepted as complex ventricular arrhythmia (CVA).

RESULTS

The mean age was 52.5+/-13.2 years; 44 (46.8%) were women. Ventricular premature contractions were detected in 80 (85.1%) patients, of whom 35 (37.2%) were classified as complex ventricular arrhythmia (CVA). Coronary artery disease, hypertension, and QTc dispersion appeared as independent factors predictive of CVA development. Atrial premature contractions (APC) were detected in 53 patients (56.4%) and supraventricular arrhythmia in 15 (16%) patients; all were identified as atrial fibrillation. Duration of dialysis therapy was found as an independent predictor of APC.

CONCLUSION

Arrhythmia is frequently observed in ESRD patients receiving hemodialysis and may be responsible for the high rate of sudden mortality. Hypertension, CAD, and QTc dispersion are independent predictors of CVA, and duration of dialysis therapy is an independent factor affecting APC development in these patients.

The Acute Cardiac Effects of Dialysis

It is well recognized that the procedure of hemodialysis is associated with significant changes in blood pressure and systemic hemodynamics; 20-30% of treatments are complicated by intradialytic hypotension (IDH). There are now an increasing number of studies using electrocardiographic, isotopic and echocardiographic techniques that show that subclinical myocardial ischemia occurs during dialysis. This concept is supported by some studies showing that dialysis can induce acute rises in troponins and creatinine kinase MB, although this has not been found by all authors. Some of this controversy may at least in part be due to the collection of blood samples immediately postdialysis, which is likely to be too early to reliably detect dialysis-induced elevations of cardiac enzymes. Cardiovascular death is the biggest single cause of mortality in dialysis patients and of this sudden death comprises the largest proportion. As such, there is a large body of evidence examining whether dialysis is pro-arrhythmogenic. It is clear that dialysis can increase QTc interval and QT dispersion and is capable of inducing arrhythmias on Holter monitoring, likely due to the interaction of multiple factors, some of which prime for the development of arrhythmias (particularly the presence of preexisting cardiac disease), and some of which act as triggers. However, the link between these electrocardiographic alterations and sudden death is relatively poorly studied. This review summarizes the available literature regarding the acute cardiac effects of dialysis in relation to the above, and discusses how these acute changes may contribute to the genesis of uremic cardiomyopathy and longer term cardiac outcomes.

Dialysis-Induced Regional Left Ventricular Dysfunction Is Ameliorated by Cooling the Dialysate

Dialysis patients who develop cardiac failure have a poor prognosis. Recurrent subclinical myocardial ischemia is important in the genesis of heart failure in nondialysis patients. It has previously been demonstrated that subclinical ischemia occurs during hemodialysis; therefore, this study examined whether the improved stability of cool-temperature dialysis lessens this phenomenon. Ten patients who were prone to intradialytic hypotension entered a randomized, crossover study to compare the development of dialysis-induced left ventricular (LV) regional wall motion abnormalities (RWMA) at dialysate temperatures of 37 and 35 degrees C. Serial echocardiography with quantitative analysis was used to assess ejection fraction and regional systolic LV function. BP and hemodynamic variables were measured using continuous pulse wave analysis. The severity of thermal symptoms was scored using a simple questionnaire. Forty-nine new RWMA developed in nine patients during hemodialysis with dialysate at 37 degrees C (HD(37)), compared with thirteen RWMA that developed in four patients during HD(35) (odds ratio 3.8; 95% confidence interval 2.1 to 6.9). The majority of RWMA displayed improved function by 30 min after dialysis. Overall, regional systolic LV function was significantly more impaired during HD(37) (P < 0.001). BP was higher during HD(35), with fewer episodes of hypotension as a result of a higher peripheral resistance and no difference in stroke volume. The development of thermal symptoms was heterogeneous, with most patients tolerating HD(35) well. This study confirms previous findings of reversible LV RWMA that develop during hemodialysis. It also shows that this phenomenon can be ameliorated by reducing dialysate temperature, a simple intervention with no cost implications.

Coronary artery disease in uremia: Etiology, diagnosis, and therapy

Cardiovascular disease is a major challenge to nephrologists, whether we deal with patients with pre-end-stage renal failure, on dialysis or after successful renal transplantation. It is the most common cause for death in patients with a functional allograft, and prevents many dialysis patients from being engrafted. Coronary artery disease is a diagnostic and therapeutic challenge, as it differs in some respects from that seen in non-uremic cohorts, and lacks much of the evidence-base on which therapeutic intervention rests. This review examines the experimental and clinical literature on cardiovascular disease in uremia, focusing on coronary artery disease. We focus on the incidence, presenting syndromes, screening tools, and interventions in the context of acute and chronic coronary syndromes. Recent evidence comparing coronary angioplasty, coronary artery stenting, and bypass surgery in subjects with renal failure is also reviewed. Coronary artery disease is more prevalent in uremia, more difficult to diagnose and less rewarding to treat compared to non-uremic subjects. Many more randomized trials are needed. In the absence of information from such trials, we advocate aggressive control of conventional and novel cardiovascular risk factors, and early intervention for symptomatic coronary disease.

Predictors of coronary disease in patients with end stage renal disease

Patients with end stage renal disease have a high prevalence of cardiovascular disease and coronary arteriography is often routinely performed prior to kidney transplantation. However, the value of the conventional risk factors and non-invasive markers of coronary artery disease (CAD) in triaging patients for coronary arteriography has not been fully examined. 116 patients with end stage renal disease were evaluated. Coronary arteriography was performed in all patients either for a suspicion of CAD or as part of a routine pre-transplant evaluation. Lesions causing > or = 50% luminal diameter stenosis in any of the three major coronary artery systems were considered significant. The mean age was 53.3 +/- 9.3 years. Significant CAD was present in 69 patients (60%). Increasing age, family history of premature ischemic heart disease, the presence of angina, abnormal Q waves on the ECG or abnormal ST segment depression and the presence of coronary calcification were significant markers of coronary artery disease. However male gender, diabetes mellitus and obesity did not correlate with coronary disease. Even though hypertension, hypercholesterolemia and smoking were also not useful predictors these could have been modified by the renal failure. In conclusion increasing age, a family history of premature ischemic heart disease and some non-invasive markers were useful predictors of coronary disease.

Anesthetic considerations for the patient with renal failure

Patients in end-stage renal disease and chronic liver failure present a number of challenges to the anesthesiologist. They may be chronically ill and debilitated and have the potential for multisystem organ dysfunction. To safely manage these patients we need to understand the benefits and limitations of dialysis and the altered pharmacology of commonly used anesthetic agents and perioperative medications in chronic renal failure.

Prediction of coronary artery disease and cardiac events using electrocardiographic changes during hemodialysis

Hemodialysis (HD) patients have a high rate of cardiac morbidity and mortality. Both symptomatic and silent ischemic heart disease may occur frequently during HD because HD simultaneously reduces coronary artery oxygen delivery while increasing myocardial oxygen demand. The purpose of the present study is to prospectively evaluate the usefulness of a significant ST depression induced by HD for the diagnosis of coronary artery disease (CAD) and as the predictor of subsequent cardiac events in HD patients. Sixty-one patients undergoing chronic HD (50 men, 11 women; mean age, 61 years) admitted for such cardiac symptoms as chest pain (n = 43), arrhythmia (n = 5), or heart failure (n = 13) were studied; 38 patients had CAD by coronary angiography. Electrocardiograms performed during HD showed an additional depression (>/=1.0 mV) of the ST segment in 18 patients (positive-ST group), but not in 43 patients (negative-ST group). The incidence of CAD was significantly greater in the former (100%) than in the latter group (46%). A prospective follow-up was performed for 21 +/- 2 months, and cardiac events occurred in all positive-ST group patients and in 21 negative-ST group patients. Event-free survival was poorer in the positive-ST group (P < 0.0001). A Cox proportional hazards model identified the significant ST depression as an independent risk factor for cardiac morbidity (P < 0.05), but not for all-cause mortality. ST depression during HD is useful to diagnose CAD in symptomatic patients and is considered an important prognosticator of subsequent cardiac events.

Current status of prevention, diagnosis, and management of coronary artery disease in patients with kidney failure

BACKGROUND

Patients with kidney failure have a heavy burden of coronary artery disease. The results of preventive, diagnostic, and therapeutic measures developed in nonuremic populations cannot automatically be extrapolated to this unique group of patients.

METHODS AND RESULTS

Articles were reviewed if they contained English language text or an abstract identified by MEDLINE search from 1980 to 1999, supplemented by manual review of bibliographies of published articles and abstract issues of national cardiology meetings, studies on diagnostic techniques, risk modification measures, pharmacologic agents, and coronary revascularization procedures in patients with uremia. Descriptive and quantitative data as appropriate were extracted. Lipid-lowering agents may be safely administered to uremic patients. Direct evidence of lipid lowering in this population is not available and is not likely to be forthcoming. Erythropoietin therapy is effective in reversing the cardiovascular perturbations of uremic anemia, but an approach of normalizing the hematocrit cannot be recommended. Glycoprotein IIb/IIIa inhibitors used in acute coronary syndromes require downward dose adjustment or are contraindicated. Thrombolytic agents are underutilized in the management of myocardial infarction. Noninvasive testing is less accurate than in nonuremic populations. Coronary revascularization offers relative clinical advantages over medical therapy similar to non-kidney failure populations, even though the results in uremic patients is significantly less favorable than for nonuremic patients. Stenting is the preferred revascularization approach, and conventional balloon percutaneous transluminal coronary angioplasty the least favorable.

CONCLUSIONS

Many but not all of the benefits of therapies developed in nonuremic patients extend to patients with kidney failure. Physicians should be familiar with the advantages and limitations of each of these modalities in this population.

Cardiac arrhythmias and silent myocardial ischemia during hemodialysis

Cardiac arrhythmias are noted in a significant proportion of chronic renal failure (CRF) patients on hemodialysis (HD), and may contribute to cardiovascular mortality. A number of factors have been implicated in the genesis of these arrhythmias. The role of silent myocardial ischemia (SMI), however, has not been evaluated systematically. We prospectively studied 38 unselected CRF patients on regular HD by continuous Holter monitoring starting 24 hours before HD, lasting through the dialysis session and continued for 20 hours thereafter. The recordings were analyzed for frequency, timing and severity of supraventricular and ventricular arrhythmias and SMI as identified by ST-segment depression. Ventricular arrhythmias during HD were noted in 11 (29%) patients (group I), and were potentially life-threatening (Lown Class III and IVa) in 13%. The remaining 27 patients (group II) had no ventricular arrhythmias during HD. There was no difference in the age, sex ratio, duration of HD, blood pressure, fluctuations in weight, hematocrit, predialysis creatinine, sodium, potassium, calcium or inorganic phosphate levels between patients in the two groups. The number of patients with clinical ischemic heart disease was significantly greater in group I. SMI was noted in 72% and 33% of group I and II patients respectively (p = 0.026). 46% of those with and 25% of those without ST changes during HD developed ventricular arrhythmias during HD. Both SMI and ventricular arrhythmias were noted most frequently during the last hour of dialysis. Hypertension, diabetes mellitus and ischemic heart disease were observed more frequently amongst patients with SMI. Ventricular arrhythmias are detected in a significant proportion of CRF patients on HD. These are probably related to coronary artery disease since silent myocardial ischemia is also noted more frequently during HD in these patients. Further studies incorporating coronary angiography are needed in a larger number of patients to establish a definite causal relationship.

Normalization of hematocrit in hemodialysis patients does not affect silent ischemia

Transient ST-segment depression measured on ambulatory ECG monitors has been described as representing silent ischemia. Patients who demonstrate silent ischemia have been reported to show increased mortality compared to patients without silent ischemia. We undertook this study to determine if the correction of anemia in End Stage Renal Disease (ESRD) patients from (+/- = standard deviation) 30 +/- 3 to 42 +/- 3 with the use of Epoietin alfa would result in decreased silent ischemia in patients with clinically evident ischemic heart disease or congestive heart failure.

METHODS

Thirty one ESRD patients with congestive heart failure or patients with clinically-evident ischemic heart disease were randomized into one of two arms. Patients in Group A had their hematocrit increased with the use of slowly escalating doses of Epoietin alfa to 42 +/- 3% and patients in Group B were maintained with a hematocrit of 30 +/- 3% throughout the course of the study. All patients had a 24 hour Holter monitor recording at baseline and at 28 weeks after randomization (when they had reached their target hematocrit). Significant silent ischemia was considered to be present if patients demonstrated at least 60 seconds of > or = 1 mm ST segment depression.

RESULTS

Fifteen patients were randomized to Group A and 16 patients were randomized to Group B. The mean hematocrit increased in group A from 29.1 +/- 2.4% to 40.8 +/- 5.2% after 30 weeks. The mean hematocrit in Group B remained stable at 30 +/- 3% throughout the course of the study. Ten patients demonstrated silent ischemia at baseline. At follow up patients in group A demonstrated a mean of 1.7 +/- 4.9 minutes of ischemia compared to 1.1 +/- 3.4 minutes in group B. These were not significantly different. A similar number of patients in group A and Group B required adjustments in their anti-anginal medication during the course of the study.

CONCLUSION

It is possible to increase hematocrit to near normal levels in hemodialysis with the administration of exogenous Epoietin alfa. The increase in hematocrit form 30 +/- 3% to 42 +/- 3% is not associated with a change in the level of silent ischemia these patients demonstrate.

[Cardiac pathology of extracardiac origin (IX)> Cardiac pathology in the patient with chronic nephropathy]

Cardiac disease constitutes a common complication among patients with renal failure. This is partly due to the high incidence of shared risk factors, such as hypertension or diabetes mellitus, and some to specific factors inherent in renal disease. It implies a high incidence of cardiac failure and ischemic heart disease (frequently without significant coronary artery obstructions) with important associated morbidity and mortality. Pericardial disease, valvular involvement and arrhythmia are also common among these patients. The management of these complications in patients with endstage renal disease has some particularities, specially in the field of drug therapy.

SILENT MYOCARDIAL ISCHEMIA IN HEMODIALYSIS PATIENTS - FACTOR FICTION?

Thirty eight patients underwent Holter ECG monitoring for a 48 hour period covering dialysis and intermediate period to detect incidence of myocardial ischemia manifesting as ST segment changes. Seventeen patients (44.7%) had 165 episodes of dynamic ST segment changes lasting from 1 to 177 minutes, with maximum ST depression of 4 mm. The mean age of patients was 45 ± 14 years and 14 (82.6%) of them were males. Ten (58.8%) patients had hypertension, and 5 (29.4%) patients each had diabetes mellitus and pre-existing coronary artery disease. Six (35.3%) patients with dynamic ST segment changes had ventricular ectopics ranging from isolated ventricular premature contractions to episodes of ventricular tachycardia. No significant hypotension or angina was documented during these episodes of ST segment deviation. We concluded that hemodialysis plays an important role in the genesis of the above ECG changes.