Prediction of hypertension in hemodialysis patients

Metformin decreased myocardial fibrosis and apoptosis in hyperhomocysteinemia -induced cardiac hypertrophy

BACKGROUND

Hyperhomocysteinemia (HHcy) is one of the major risk factors of cardiovascular diseases. Metformin acts as a cardioprotective role in several cardiovascular diseases, including ischemia/reperfusion, atherosclerosis, and myocardial infarction. However, whether metformin protects against HHcy-induced cardiac hypertrophy is unclear.

METHODS AND RESULTS

HHcy model was established in C57BL/6 mice with high L-methionine (L-MET) diet for 12 weeks. AC16 cells were exposed to homocysteine (Hcy) and then intervened with different concentrations of metformin in in vitro studies. The results showed that HHcy was able to induce cardiac hypertrophy, and metformin could abrogate this effect. HHcy increased the fibrosis area and induced apoptosis in the myocardium, whereas metformin could reverse the detrimental effects above. TUNEL assay showed that metformin was able to decrease Hcy-induced apoptosis in AC16 cells. Moreover, western blotting assay revealed that metformin could decrease Hcy-induced expression of Bax and cleaved caspase3, and increase the expression of Bcl-2.

CONCLUSIONS

This study demonstrates that metformin is able to attenuate HHcy-induced cardiac hypertrophy by decreasing myocardial fibrosis and apoptosis.

Hypertension as a cardiovascular risk factor in end-stage renal failure

There is a paucity of high quality studies on the prognostic importance of arterial pressure in end-stage renal disease. Furthermore, the optimal timing for blood pressure (BP) measurements (pre- or postdialysis), and the prognostic value of 24-hour ambulatory BP monitoring in these patients remain to be established. In end-stage renal disease patients without diabetes and heart failure, predialysis systolic, diastolic, and pulse pressure are strongly and independently related to left ventricular mass, and the strength of these relationships is higher than that between the corresponding postdialysis values and left ventricular mass. Average predialysis systolic pressure (monthly average) is associated with left ventricular mass as strongly as 24-hour systolic BP, which suggests that the average routine predialysis BP taken over 1 month may be equally representative of the "true" BP (the integrated BP load) than 24-hour ambulatory BP monitoring. Mortality is U shaped in large hemodialysis databases. In the only prospective study that adequately controlled for cardiac function at baseline, it was shown that hypertension is associated with a higher risk of developing congestive heart failure, and that patients with left ventricular hypertrophy or chronic heart failure are at a much higher risk of mortality than patients without these complications. The role of arterial stiffening (pulse pressure) as a cardiovascular risk factor has been firmly established in an analysis of a very large dialysis database in the United States, and by recent studies based on direct measurements of pulse wave velocity.

Assessment of blood pressure in hemodialysis patients

It is self-evident that accurate measurement of blood pressure (BP) is essential for the diagnosis and treatment of hypertension. Patients on hemodialysis typically do not have their BP measured under standardized conditions, a source of error in the assessment of their BP. However, their are some unique sources of error involving interdialytic weight gain, occurrence of sleep apnea and consequent nocturnal hypertension, inability to take BP in both arms in patients who have hemodialysis angioaccess in the arm, and the white coat effect in these patients as well. Precise measurement of BP in hemodialysis patients requires interdialytic ambulatory BP monitoring. However, when ambulatory BP monitoring is not possible, BP obtained in the dialysis unit can be used in a qualitative sense for prediction of hypertension in these patients. A 2-week average predialysis BP of greater than 150/85 mmHg or a postdialysis BP of greater than 130/75 mmHg has at least 80% sensitivity in diagnosing hypertension. Specificity of at least 80% can be achieved if predialysis BP of greater than 160/90 mmHg or postdialysis BP of greater than 140/80 mmHg are used. However, poor agreement between hemodialysis unit BP and ambulatory BP precludes their use for the precise prediction of BP. Improving measurement techniques in the dialysis unit, averaging multiple BP values, using 20-minute postdialysis readings, or home BP monitoring can improve BP determination when interdialytic BP monitoring is not possible.

Ambulatory blood pressure monitoring in chronic renal disease: technical aspects and clinical relevance

PURPOSE OF REVIEW

To evaluate the current value of ambulatory blood pressure monitoring in patients with chronic renal disease and end-stage renal disease.

RECENT FINDINGS

Ambulatory blood pressure monitoring has become an important tool in hypertension research and clinical practice. Its use in essential hypertension shows a strong predictive ability in the assessment of cardiovascular outcomes. In chronic renal failure and end-stage renal disease, the role of ambulatory blood pressure monitoring is still being actively evaluated, and available evidence shows that it is better than office blood pressure in predicting left ventricular hypertrophy and progression of renal dysfunction in patients with chronic renal failure. In end-stage renal disease, preliminary data suggest better prediction of mortality in hemodialysis patients in comparison with clinic blood pressures. The most conspicuous problems with the literature on this subject are small sample sizes and the paucity of longitudinal observational studies and intervention trials.

SUMMARY

Preliminary data and extrapolations from essential hypertension have justified a growing excitement about the use of ambulatory blood pressure monitoring in renal disease. However, further research will have to address the limitations of the available literature before generalization of its use is implemented.