Applicability and clinical relevance of the transfer function method in the assessment of baroreflex sensitivity in heart failure patients.
OBJECTIVE
We sought to assess applicability, clinical correlates, and prognostic value of the transfer function method for measuring baroreflex sensitivity (TF-BRS).


BACKGROUND
Abnormalities in autonomic reflexes play an important role in the development and progression of chronic heart failure (CHF). Simple and non-invasive techniques for clinical measurement of such reflexes are desirable.


METHODS
In 317 stable CHF patients in sinus rhythm (median age [interquartile range]: 54 years [48 to 59 years], New York Heart Association [NYHA] functional class II to III: 88%, left ventricular ejection fraction [LVEF]: 27% [22% to 33%]) we recorded electrocardiograms and non-invasive arterial pressure during paced breathing to measure TF-BRS.


RESULTS
Owing to a high number of ectopic beats, TF-BRS could be computed in 72% of the patients; TF-BRS was lower in NYHA functional class III to IV and mitral regurgitation 2 to 3 (p < 0.0005 for both). Correlation with LVEF and standard deviation of all normal-to-normal intervals was 0.18 and 0.31 (p < 0.001 for both). During a mean follow-up of 26 months, 23% of the patients experienced a cardiac event. A depressed TF-BRS (< or =3.1 ms/mm Hg) was significantly associated with the outcome (hazard ratio 3.2, 95% confidence interval [CI] 1.7 to 6.0, p = 0.0003). Patients with a missing TF-BRS had a high event rate (36%). Combining this information with available TF-BRS measurements, a new prognostic index could be computed in 97% of the patients that significantly predicted the outcome after adjustment for clinical and functional variables (hazard ratio 2.5, 95% CI 1.3 to 4.6 p = 0.004).


CONCLUSIONS
In CHF patients in sinus rhythm, TF-BRS conveys relevant clinical and prognostic information, but its measurability is markedly affected by ectopic activity. Nevertheless, a TF-BRS-based risk index carrying significant and independent prognostic information can be computed in almost all patients.
Pinna
Gian Domenico
GD
Department of Cardiology and Biomedical Engineering, Salvatore Maugeri Foundation, IRCCS, Scientific Institute of Montescano, Montescano, PV, Italy. gdpinna@fsm.it
Maestri
Roberto
R
Capomolla
Soccorso
S
Febo
Oreste
O
Robbi
Elena
E
Cobelli
Franco
F
La Rovere
Maria Teresa
MT
D017704:Baroreflex / Q000502:physiology*; D003943:Diagnostic Techniques, Neurological; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D018570:Risk Assessment