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CLINICAL RESEARCH: CARDIAC IMAGING

Cardiac Iodine-123 Metaiodobenzylguanidine Imaging Predicts Sudden Cardiac Death Independently of Left Ventricular Ejection Fraction in Patients With Chronic Heart Failure and Left Ventricular Systolic Dysfunction

Results From a Comparative Study With Signal-Averaged Electrocardiogram, Heart Rate Variability, and QT Dispersion

Shunsuke Tamaki, MD^_*,_*, Takahisa Yamada, MD^_*, Yuji Okuyama, MD^_*, Takashi Morita, MD^_*, Shoji Sanada, MD^_*, Yasumasa Tsukamoto, MD^_*, Masaharu Masuda, MD^_*, Keiji Okuda, MD^_*, Yusuke Iwasaki, MD^_*, Taku Yasui, MD^_*, Masatsugu Hori, MD and Masatake Fukunami, MD^_*

^_* Division of Cardiology, Osaka General Medical Center, Osaka, Japan
Department of Cardiovascular Medicine, Osaka University Graduate School of Medicine, Osaka, Japan

Manuscript received April 7, 2008; revised manuscript received October 20, 2008, accepted October 26, 2008.

^_* Reprint requests and correspondence: Dr. Shunsuke Tamaki, Division of Cardiology, Osaka General Medical Center, 3-1-56, Mandai-Higashi, Sumiyoshi-ku, Osaka 558-8558, Japan (Email: tamaki-shunsuke{at}mwc.biglobe.ne.jp).

Objectives: We prospectively compared the predictive value of cardiac iodine-123 metaiodobenzylguanidine (MIBG) imaging for sudden cardiac death (SCD) with that of the signal-averaged electrocardiogram (SAECG), heart rate variability (HRV), and QT dispersion in patients with chronic heart failure (CHF).

Background: Cardiac MIBG imaging predicts prognosis of CHF patients. However, the long-term predictive value of MIBG imaging for SCD in this population remains to be elucidated.

Methods: At entry, cardiac MIBG imaging, SAECG, 24-h Holter monitoring, and standard 12-lead electrocardiography (ECG) were performed in 106 consecutive stable CHF outpatients with a radionuclide left ventricular ejection fraction (LVEF) <40%. The cardiac MIBG washout rate (WR) was obtained from MIBG imaging. Furthermore, the time and frequency domain HRV parameters were calculated from 24-h Holter recordings, and QT dispersion was measured from the 12-lead ECG.

Results: During a follow-up period of 65 ± 31 months, 18 of 106 patients died suddenly. A multivariate Cox analysis revealed that WR and LVEF were significantly and independently associated with SCD, whereas the SAECG, HRV parameters, or QT dispersion were not. Patients with an abnormal WR (>27%) had a significantly higher risk of SCD (adjusted hazard ratio: 4.79, 95% confidence interval: 1.55 to 14.76). Even when confined to the patients with LVEF >35%, SCD was significantly more frequently observed in the patients with than without an abnormal WR (p = 0.02).

Conclusions: Cardiac MIBG WR, but not SAECG, HRV, or QT dispersion, is a powerful predictor of SCD in patients with mild-to-moderate CHF, independently of LVEF.

Key Words: cardiac I-123 metaiodobenzylguanidine imaging • chronic heart failure • sudden cardiac death

Abbreviations and Acronyms   AUC = area under the curve   CHF = chronic heart failure   ECG = electrocardiography/electrocardiogram   fQRSd = the duration of filtered QRS complex   H/M = heart-to-mediastinum ratio   HRV = heart rate variability   LAS40 = the duration of low-amplitude signals <40 µV in the terminal portion of filtered QRS complex   LVEF = left ventricular ejection fraction   MIBG = metaiodobenzylguanidine   NN = normal-to-normal   NYHA = New York Heart Association   QTc = corrected QT interval   RMS40 = the root mean square voltage for the last 40 ms of filtered QRS complex   ROI = region-of-interest   SAECG = signal-averaged electrocardiogram   SCD = sudden cardiac death   WR = washout rate

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