Methods

The registry of all adult patients (aged ≥18 years) referred for evaluation of heart failure at the Heart Failure Care Unit, Fuwai Hospital, from October 2008 to November 2012 was reviewed to identify ROCM. The diagnosis of DCM was made according to the recommendations on diagnosis and treatment of cardiomyopathy (China) in 2007. All patients had an LVEF of ≤40% by echocardiography and symptom duration of <6 months at presentation, in the absence of significant coronary artery disease, primary restrictive, or hypertrophic cardiomyopathy, primary valvular, or congenital heart disease. Patients on cardiac resynchronization therapy were excluded, because we focused on the effect of medication alone. Patients with known cardiomegaly for >6 months were not considered to have ROCM regardless of symptom duration. However, patients in whom a history of hypertension or alcohol use was documented in the medical records were included because in an individual patient it is often unclear whether these factors cause, exacerbate, or have no relation to the development of cardiomyopathy.

An array of clinical and echocardiographic variables regarded as potentially relevant to normalization of LVEF was evaluated on admission. Transthoracic echocardiography was performed in all patients at baseline, and LVEF was measured using the modified Simpson method. All patients were clinically followed up at least 12 months or until cardiac transplantation or death, at intervals of 3 to 6 months by telephone interview or on outpatient clinic visit, depending on severity of illness and involvement of the referring physician. Repeat echocardiography was performed within 3 months after discharge when possible, every 6 to 12 months thereafter, and whenever clinically indicated. Normalization of LVEF was defined as an increase in LVEF to a final level of ≥50% by echocardiography during follow-up. This study was approved by local ethics committees of Fuwai Hospital.

Continuous variables are expressed as mean ± SD or median (interquartile range) and categorical variables as percentage. For group comparisons, the Student t test or Mann-Whitney U test for continuous variables and chi-square test or Fisher’s exact test for categorical variables were used. Changes in variables from baseline to follow-up in each group were compared using paired Student t test. Risk estimation associated with normalization of LVEF was performed using univariate and multivariate logistic regression models with forward conditional (stepwise) method. After the final model was derived, it was tested for calibration using the Hosmer-Lemeshow chi-square test, and capacity of discrimination was tested using the area under the receiver operating characteristic curve. All tests were 2-tailed, and a significant difference was considered at the p <0.05. Statistical analysis was performed using the SPSS 19.0 statistical software package (SPSS, Inc., IBM, Armonk, New York).

Results

A consecutive cohort of 176 patients with ROCM was reviewed during the period, and 128 patients were enrolled in the final analysis. The study flow diagram is shown in Figure 1 .

Flow diagram of included subjects. CRT-P/D = cardiac resynchronization therapy–pacemaker/defibrillator.

The mean age of study subjects was 43 ± 14 years. At baseline, LVEF was 30 ± 6%, left ventricular end-diastolic diameter (LVEDD) was 66 ± 7 mm, symptom duration was 1.9 ± 1.4 months, and percentage of New York Heart Association functional class II, III, and IV on admission was 14%, 59%, and 27%, respectively.

Therapy on discharge included a β blocker in 95%, an angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB) in 84%, spironolactone in 96%, digoxin in 79%, and loop diuretics in 100% of patients. Baseline characteristics are summarized in Table 1 .

After a mean follow-up of 31 ± 13 months (range 1 to 59), 62 patients (48%) normalized their LVEF, showing a significant increase in LVEF from 32 ± 6% at baseline to 58 ± 5% at follow-up (p <0.001), with a mean increase of 26 ± 8% ( Figure 2 ). This increase in LVEF was associated with a marked decrease in LVEDD from 63 ± 5 to 52 ± 4 mm (p <0.001; Figure 3 ).

Normalization of LVEF. LVEF at baseline (p <0.001), at last follow-up (p <0.001), and change from baseline to follow-up (p <0.001) were all significantly greater in patients with normalization of LVEF than those without normalization.

Decrease in LVEDD. In patients with normalization of LVEF, LVEDDs at baseline (p <0.001) and at the last follow-up (p <0.001) were smaller, and the decrease in LVEDD from baseline to last follow-up was greater than in those without normalization.

The shortest time from diagnosis to normalization was 1 month and the longest was 39 months, with a median time of 6 months. Moreover, 68% (n = 42) patients normalized their LVEF within 1 year after initial diagnosis.

On univariate analysis, normalization of LVEF was significantly associated with a history of hypertension, higher systolic blood pressure (SBP) at presentation, shorter QRS duration and absence of left bundle branch block on electrocardiogram, smaller LVEDD and lower LVEF by echocardiography, and higher serum sodium level ( Table 2 ).

Multivariate analysis demonstrated that a history of hypertension (odds ratio [OR] 3.278, p = 0.030), higher SBP at presentation (OR 1.041, p = 0.002), shorter QRS duration (OR 0.975, p = 0.019), smaller LVEDD (OR 0.914, p = 0.001), and higher LVEF (OR 1.123, p = 0.005) by echocardiography at baseline were significantly independent predictors of normalization ( Table 2 ). Accordingly, patients with a history of hypertension, presenting with higher SBP, shorter QRS duration, smaller echocardiographic LVEDD, and higher LVEF at baseline were associated with a higher likelihood of subsequent normalization of LVEF.

Finally, the optimal model to predict normalization of LVEF, written as the logit (linear exponential term of the logistic model), was:

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