TORONTO—Researchers have taken another step toward understanding why reduced kidney function gives patients with stable heart failure a significantly increased risk of dying.
A team has found that increased cardiac filling pressure represented by right ventricular systolic pressure (RVSP) and natriuretic peptide (NT-proBNP) is tied strongly to increased serum creatinine and reduced estimated glomerular filtration rate (eGFR). They did not find, however, an association between left ventricular ejection fraction (LVEF) and kidney function, which surprised investigators because previous studies have shown that a lower LVEF is associated with reduced renal perfusion and thus leads to renal insufficiency. They hope to repeat the study with a larger number of patients to see if the findings change or remain the same.
“At this point, we are just trying to determine whether there are relationships, and now we have to do more research to understand the details,” said Carlos Fernando, MD, who presented the results at the 2012 Canadian Cardiovascular Congress.
Dr. Fernando, who is a graduate student at the University of Toronto, worked with lead investigator Gordon Moe, MD, a cardiologist at St. Michael’s Hospital in Toronto, and other colleagues to tease out the links between renal insufficiency and heart failure. Heart failure patients with moderate to severe renal dysfunction have at least a twofold increase in relative mortality risk. A recent study published in the Journal of Cardiology (2012;60:301-305) has shown that treating heart failure can improve kidney function and, in turn, lower mortality.
To explore the associations between renal factors and cardiac parameters, the researchers followed 246 patients with stable chronic heart failure who were being treated at the St. Michael’s Hospital heart failure program. They assessed patients’ LVEF and RVSP,echocardiographically; serum creatinine, eGFR and levels of the heart-failure biomarker N-terminal pro-hormone of brain natriuretic peptide (NT-proBNP). The team did not examine other parameters derived from echocardiography, such as wedge pressure. The patients’ median RVSP was 40.5 mm Hg, median NT-proBNP level was 1,614 pg/mL, median serum creatinine level was 104 µmol/L, and median eGFR was 57.5. The median LVEF was 35%.
Both RVSP and NT-proBNP were significantly correlated with serum creatinine and eGFR. In contrast, LVEF was not correlated with either of these kidney function measures.
Subjects’ mean blood pressure was 120.5 mmHg/67.4 mmHg, their average age was 69 years, and 72% were men. The majority were Caucasians, at 63.8%, while 31.3% were Asians and 4.9% were African Canadians. In all, 69.1% were New York Heart Association Class II heart failure and 29.3% Class III. Only 1.6% had Class IV heart failure. Approximately 90% had been prescribed loop diuretics and about 70% were on ACE inhibitors.