Heart Rate Variability Density Analysis (Dyx) and Prediction of Long-Term Mortality after Acute Myocardial Infarction.
OBJECTIVE
The density HRV parameter Dyx is a new heart rate variability (HRV) measure based on multipole analysis of the Poincaré plot obtained from RR interval time series, deriving information from both the time and frequency domain. Preliminary results have suggested that the parameter may provide new predictive information on mortality in survivors of acute myocardial infarction (MI). This study compares the prognostic significance of Dyx to that of traditional linear and nonlinear measures of HRV.


RESULTS
In the Nordic ICD pilot study, patients with an acute MI were screened with 2D echocardiography and 24-hour Holter recordings. The study was designed to assess the power of several HRV measures to predict mortality. Dyx was tested in a subset of 206 consecutive Danish patients with analysable Holter recordings. After a median follow-up of 8.5 years 70 patients had died. Of all traditional and multipole HRV parameters, reduced Dyx was the most powerful predictor of all-cause mortality (HR 2.4; CI 1.5 to 3.8; P < 0.001). After adjustment for known risk markers, such as age, diabetes, ejection fraction, previous MI and hypertension, Dyx remained an independent predictor of mortality (P = 0.02). Reduced Dyx also predicted cardiovascular death (P < 0.01) and sudden cardiovascular death (P = 0.05). In Kaplan-Meier analysis, Dyx significantly predicted mortality in patients both with and without impaired left ventricular systolic function (P < 0.0001).


CONCLUSIONS
The new nonlinear HRV measure Dyx is a promising independent predictor of mortality in a long-term follow-up study of patients surviving a MI, irrespectively of left ventricular systolic function.
Department of Cardiology, Copenhagen University Hospital Gentofte, Denmark.
Rikke Mørch
RM
Jørgensen
Department of Cardiology, Bispebjerg Hospital, Copenhagen, Denmark.
Steen Z
SZ
Abildstrøm
Department of Physics, Ariel University, Samaria, Israel.
Jacob
J
Levitan
Department of Physics, Ariel University, Samaria, Israel.
Roi
R
Kobo
Department of Physics, Ariel University, Samaria, Israel.
Natalia
N
Puzanov
Department of Physics, Ariel University, Samaria, Israel.
Meir
M
Lewkowicz
Department of Internal Medicine, University of Oulu, Finland.
Heikki
H
Huikuri
Department of Internal Medicine, University of Oulu, Finland.
Mirja
M
Peltola
Department of Cardiology, Copenhagen University Hospital Gentofte, Denmark.
Jens
J
Haarbo
Department of Cardiology, Aalborg University Hospital, Aalborg, Denmark.
Poul Erik Bloch
PE
Thomsen
D000368:Aged; D004452:Echocardiography; D015716:Electrocardiography, Ambulatory; D005260:Female; D005500:Follow-Up Studies; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000401:mortality* / Q000503:physiopathology; D010865:Pilot Projects; D011237:Predictive Value of Tests; D011379:Prognosis
Dyx; Poincaré plot; heart rate variability; multipoles; myocardial infarction