CLINICAL STUDY: HEART FAILURE
Prognostic value of mechanical efficiency in ambulatory patients with idiopathic dilated cardiomyopathy in sinus rhythm
I. l Sung Kim, MD*,
Hideo Izawa, MD, PhD ,
Toshikazu Sobue, MD, PhD,
Hitoshi Ishihara, MD, PhD,
Fuji Somura, MD,
Takao Nishizawa, MD*,
Kohzo Nagata, MD, PhD,
Mitsunori Iwase, MD, PhD and
Mitsuhiro Yokota, MD, PhD, FACC*,*
* Cardiovascular Division, Department of Clinical Pathophysiology, Nagoya University Graduate School of Medicine, Nagoya, Japan
First Department of Internal Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan
Nagoya University School of Health Science, Nagoya, Japan
Manuscript received August 7, 2001;
revised manuscript received January 7, 2002,
accepted January 18, 2002.
* Reprint requests and correspondence: Dr. Mitsuhiro Yokota, Department of Clinical Laboratory Medicine, Nagoya University Hospital, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8560, Japan.
myokota{at}med.nagoya-u.ac.jp
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Abstract
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OBJECTIVES: The purpose of this study was to determine, by analyzing the pressure-volume relationship, the prognostic value of parameters related to myocardial energetics for predicting mortality in patients with dilated cardiomyopathy (DCM) in sinus rhythm.
BACKGROUND: The relationship between the myocardial energetics and the prognosis of patients with DCM in sinus rhythm remains unclear.
METHODS: We followed 114 ambulatory patients with nonischemic DCM in sinus rhythm for a mean period of 5.8 ± 3.9 years. Over 70% of our patients were in New York Heart Association functional class I and class II. Pressure-volume data were obtained by the conductance method, and myocardial oxygen consumption per beat (VO2) measurements were obtained.
RESULTS: The 3-, 5-, and 10-year cumulative survival rates were 88.6%, 80.0%, and 73.9%, respectively. Of the 114 patients, 47 were selected randomly to assess their myocardial energetics. By univariate analysis, the mechanical efficiency (ME, external work/VO2), left ventricular (LV) ejection fraction and the LV end-diastolic pressure were statistically associated with cardiac death. The ME was the strongest predictor of survival in a Cox proportional-hazards analysis (p = 0.011). The best cutoff point of ME identified by the receiver-operating curve was 11%. This value had a sensitivity of 100%, a specificity of 87% and an overall predictive accuracy of 88% to distinguish survivors from nonsurvivors.
CONCLUSIONS: This study clearly demonstrates that ME is a powerful clinical predictor for cardiac death in patients with mild to moderate heart failure and with sinus rhythm. Whether these conclusions apply to patients with more severe heart failure requires further investigations.
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Abbreviations and Acronyms
| | AF | | atrial fibrillation | | DCM | | dilated cardiomyopathy | | Ees | | end-systolic elastance | | EW | | external work | | LV | | left ventricular/ventricle | | LVEF | | left ventricular ejection fraction | | ME | | mechanical efficiency | | PVA | | pressure-volume area | | VO2 | | myocardial oxygen consumption per beat |
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Dilated cardiomyopathy (DCM) is characterized by progressive left ventricular (LV) dilation and severely depressed LV systolic function. It eventually culminates in end-stage congestive heart failure and cardiac death (1,2). Therefore, it is essential to identify, as early as possible, patients who are unlikely to improve or stabilize with standard medical treatment. Several studies have attempted to find clinical and laboratory abnormalities associated with poorer prognosis. These have included indices related to LV systolic and diastolic function such as LV ejection fraction (LVEF), LV end-diastolic dimensions and pressures and transmitral inflow characteristics (2–5). One of the limitations of these markers, however, is their load-dependence (6), which may confound accurate assessment of LV systolic or diastolic function and limit their predictive value. Recent studies have focused on myocardial energetics as well as myocardial function to elucidate the pathophysiology of DCM (7–10). Analysis of the pressure-volume relationship provides a better understanding of the myocardial energetics and enables a fuller appreciation of the impaired energy generation in the diseased heart, which may be associated with a poor prognosis in patients with DCM. However, no previous studies have evaluated the relationship between myocardial energetics and the prognosis of patients with DCM.
Atrial fibrillation (AF) is common in patients with DCM and is associated with a variety of potentially deleterious hemodynamic consequences that might exert a negative influence on prognosis and accelerate the progression of LV systolic dysfunction (11,12). The overall survival rate for patients in sinus rhythm has been found to be higher than the rate for patients with AF (13). However, the prognostic indicators in patients with DCM in sinus rhythm remain unclear.
Accordingly, the purpose of this study was to determine the prognostic value of myocardial energetics for predicting mortality in patients with DCM in sinus rhythm by directly measuring myocardial oxygen consumption and analyzing the pressure-volume relationship.
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Methods
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Patient population.
The study population consisted of 114 consecutive ambulatory patients with nonischemic DCM in sinus rhythm who were referred to Nagoya University Hospital between February 1983 and October 1999. Dilated cardiomyopathy was defined as a decreased LVEF (<50% as determined by contrast ventriculography) and a dilated LV cavity in the absence of significant coronary artery stenosis (>50% as determined by coronary angiography) or valvular heart disease, arterial hypertension, or cardiac muscle disease caused by any known systemic disease (14). A right or left ventricular biopsy was obtained to confirm the diagnosis of DCM. Patients with AF were excluded. The drug regimen at baseline consisted of diuretics in 51 patients (46%), digitalis in 52 (47%), angiotensin-converting enzyme (ACE) inhibitors in 37 (34%) and beta-blockers in four (4%). Medical therapy during follow-up was determined by the referring physicians and was based on the clinical symptoms and course of the disease, but there was no difference in beta-blocker use or ACE inhibitor use over the course of the study. The study protocol was approved by the appropriate institutional review committee. Each patient gave written informed consent before entering the study.
Cardiac catheterization.
All medications were withheld for the three days before the study. Selective coronary angiography, left ventriculography, and cardiac biopsy were performed by the femoral approach to confirm the diagnosis of DCM. Of the 114 patients, 47 were selected randomly to assess myocardial energetics. Because accurate assessment of LV energetics requires an invasive protocol with extensive instrumentation, we aimed to prove a prognostic value of myocardial energetics using the minimum number of patients. A double-thermister catheter (model CCS/GOK, Hilton-Webster Laboratories, Baldwin Park, California) was placed in the coronary sinus through the brachial or subclavian vein to measure myocardial blood flow. After left ventriculography, when LV end-diastolic pressure returned to baseline values, an eight-electrode volume conductance catheter with a micromanometer tip (Leycom, Zoetermeer, The Netherlands) was advanced to the LV to measure the LV volume and pressure. A Fogarty catheter was placed in the inferior vena cava and inflated transiently to determine the LV end-systolic pressure-volume relationship. Arterial and coronary sinus blood samples were drawn simultaneously to measure the oxygen saturation.
The LV pressure-volume data analysis.
A volume-conductance catheter was connected to a volumetric system (model Sigma 5, Leycom, Oestgeest, The Netherlands) to measure the LV volume conductance and convert it to the LV volume. The LV volume obtained by the conductance method was calibrated by biplane ventriculography (area-length method) as described previously (8,9). An end-systolic pressure-volume line was drawn on the left upper corner of the pressure-volume loops of the initial 5 to 14 contractions during the transient decrease in preload caused by the inflation of a Fogarty catheter. The LV contractility index (Ees) was defined as the slope of the end-systolic pressure-volume line (15). The pressure-volume area (PVA) was defined as the area under the end-systolic pressure-volume line and the systolic pressure-volume trajectory and the end-diastolic pressure-volume relation curve. External work (EW) was defined as the area within the pressure-volume diagrams. The PVA and EW were measured in millimeters of mercury (mm Hg) times milliliters and converted to the dimensions of energy using the following formula:
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(16)
Myocardial oxygen consumption.
Myocardial blood flow was measured using a double-thermister catheter. The coronary sinus flow was calculated according to the method of Ganz et al. (17) using a computer system as described in previous studies (8,9). Myocardial oxygen consumption per minute was calculated as the product of coronary sinus flow and the arterial-coronary sinus oxygen content difference. Myocardial oxygen consumption per beat (VO2) was calculated as follows:
where 1 ml O2 = 20 J (16). Mechanical efficiency (ME) was defined as the dimensionless ratio of EW to VO2.
Clinical and follow-up data.
Demographic data at study entrance were assessed by review of the visit and hospital records. Survival and symptomatic status at follow-up were also determined from review of this visit and hospital records, when available, or by telephone contact with patients, relatives, or the referring physician. A standard questionnaire was used for the follow-up interviews.
Statistical analysis.
Data are expressed as the mean value ± SD. Differences between survivors and nonsurvivors were assessed using the unpaired t test, or chi-square analysis, as appropriate. Cumulative survival estimates were calculated using the Kaplan-Meier method, with differences between the survival curves assessed by the log-rank test. To identify the independent predictors of survival, the Cox proportional hazards survival model was performed at the significant variables by stepwise multiregression analysis. Receiver-operating characteristic curves were constructed, and a jackknife procedure was used to assess how well the cutoff worked. A p value < 0.05 was considered statistically significant.
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Results
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Patient characteristics.
Patients were followed for an average of 5.8 years (range 0.7 to 10.9 years) starting from the catheterization and ending with a cardiac event or the most recent data on the survivors. During the follow-up period, a total of 114 patients (range 23 to 65 years; mean age 50 ± 12 years) were followed. Of these patients, four were excluded because they died of non-cardiac causes. Nineteen died of cardiac causes (16 patients with progressive heart failure and 3 with sudden death). The 3-, 5- and 10-year cumulative survival rates were 88.6%, 80.0% and 73.9%, respectively (Fig. 1). There were no differences in the number of patients with a familial history of DCM or sudden death, exercise duration during treadmill tests, or the occurrence of ventricular tachycardia between the survivors and nonsurvivors.
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Figure 1 Kaplan-Meier survival curves for cardiac mortality of a larger cohort of 110 patients (A), those of 47 selected patients who underwent myocardial energetics measurements (B) and those of patients grouped according to mechanical efficacy (ME) (C: ME  11%, D: ME <11%).
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Hemodynamics and myocardial energetics.
We randomly selected 47 of the 114 patients to assess the parameters of myocardial energetics. None of the selected 47 patients died of non-cardiac causes. The selected group of 47 patients had a somewhat better prognosis than the entire group of 110 patients, although the difference was not significant (p = 0.24; Fig. 1). There was no difference in the clinical and hemodynamic characteristics between the entire group of 110 patients and the selected group of 47 patients (Table 1). In the selected group, the LVEF was 37.1 ± 12.0%, the Ees was 1.20 ± 0.64 mm Hg/ml, and the ME (EW/VO2) was 20.8 ± 14.2%. These values were lower than normal in our laboratory (18–20). There were significant differences in the LVEF, the maximum first derivative of LV pressure (LV dP/dt max), effective arterial elastance, PVA, EW, VO2 and myocardial energy conversion (PVA/VO2) between the survivors and nonsurvivors (Table 2). In addition, the ME in the nonsurvivors was extremely depressed compared with the survivors (8.5 ± 2.2% vs. 22.7 ± 15.1%, respectively).
Univariate analysis of nonsurvivors.
The findings of the stepwise linear regression analysis for predicting mortality from the measured variables indicated that the best predictors of mortality were the ME (chi-square to remove 5.53; p < 0.01), LVEF (chi-square to remove 7.06; p < 0.01) and LV end-diastolic pressure (chi-square to remove 4.75; p < 0.01). Cox proportional-hazard regression analysis was performed on ME, LVEF and LV end-diastolic pressure. Mechanical efficiency was the most important and independent variable for predicting survival (p = 0.011). The LVEF and LV end-diastolic pressure were the next best predictive variables but were not significant (p = 0.058, p = 0.884, respectively).
Prognostic significance of mechanical efficiency.
To evaluate the further prognostic significance of the ME, a receiver operating characteristic curve was constructed, and it indicated that the best cutoff value for the ME was 11%. This value had a sensitivity of 100%, a specificity of 87% and an overall predictive accuracy of 88% in distinguishing survivors from nonsurvivors using the jackknife procedure. The patients whose ME was <11% had a significantly reduced five-year survival rate of 58.3% compared with those whose ME was 11%, who had a five-year survival rate of 100% (p < 0.001; Fig. 1).
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Discussion
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Despite recent improvements in the medical management of patients with DCM, the overall prognosis is still poor, and heart transplantation often represents the only lifesaving therapeutic option for these patients (1,2,4). Several investigators (2–5) have tried to identify prognostic factors that might predict a poor outcome in these patients in an attempt to select patients appropriately for heart transplantation or for more aggressive forms of treatment. Unfortunately, no factor has proven to predict unequivocally the risk of cardiac death or the need for heart transplantation. This study is the first to report that an ME 11% is an independent clinical predictor for survival in patients with mild to moderate DCM in sinus rhythm.
Mechanoenergetic uncoupling in DCM.
The ME of the LV is defined as the fraction of total expended metabolic energy that is converted into external contractile work (21). The concept of ME includes information not only about cardiac output but also about the concomitant energy cost. Mechanical efficiency has been used mainly to assess and optimize the effects of medical therapy in patients with heart failure, and it has been suggested that ME is a very sensitive parameter for characterizing LV performance by taking into account the energy cost for a given level of cardiac output (8,9,22), which may support our current findings. In heart failure, the oxygen cost of contraction remains relatively unchanged, despite markedly impaired LV work, resulting in a decrease in the ME of contraction. In fact, in the present study, patients with mild to moderate DCM in sinus rhythm showed a remarkable decrease in the ME defined as the ratio of external work to myocardial oxygen consumption. Therefore, patients with DCM are characterized by mechanoenergetic uncoupling, which is an imbalance between LV performance and myocardial energy consumption.
Comparison with previous studies.
In most studies of survival in DCM, the LVEF is undoubtedly the factor that has received the most attention (2–4). In previous studies, the LVEF was the single independent prognostic factor, although other studies either did not support this observation (23,24) or found that the LVEF was less predictive than other parameters such as the Doppler-derived dP/dt (25) or the transmitral inflow characteristics (5). In a previous study (4), an LVEF <20% was associated with a one-year mortality of 30% in patients with DCM. Actually, both the LVEF and the directly measured peak-positive dP/dt were significantly higher in survivors than in nonsurvivors in the present study. However, we could not confirm these variables to be significant prognostic predictors. These differences may be explained by differences in the patient populations. It is noteworthy that our patients showed a favorable prognosis; the 5-year mortality was 20%, and the 10-year mortality was 26%. Our study consisted of a less severely afflicted, ambulatory population of patients whose mean LVEF was about 40% and had sinus rhythm. Over 70% of our patients were in New York Heart Association (NYHA) functional class I and II, but most previous studies were based on an analysis of patients in NYHA functional class III and IV. In addition, most previous studies included patients with AF.
Recent data in humans (11) have demonstrated that the persistent irregularity in ventricular cycle lengths resulting from AF adversely affects ventricular function and the hemodynamic status, independent of the effect of AF upon the ventricular rate. More recently, the presence of AF with heart failure has been demonstrated (12) to be independently associated with an increased risk for mortality. Thus, we believe that our study is the first to demonstrate clearly that ME is an important and powerful prognostic predictor in clinically stable and ambulatory patients with DCM in sinus rhythm.
Study limitations.
Several methodological problems must be discussed. First, the number of patients enrolled in the present study was relatively small. In addition, this study was performed in clinically stable and ambulatory patients in sinus rhythm. Therefore, the results cannot be widely extrapolated to patients with more severe LV dysfunction. Further studies of larger numbers of patients are needed before these conclusions can be applied more generally to patients with LV dysfunction. Second, we assumed that the LV volume obtained by the conductance catheter could be reliable. It has been reported that the conductance catheter may underestimate real volume when calibrated by using blood conductivity and measuring parallel conductance by injection of hypertonic saline solution (26,27). However, in our previous study (8), we demonstrated the reproducibility of measurements obtained by the same method as in the present study. Furthermore, other methods of measuring LV volume, such as two-dimensional echocardiogram or radioisotope angiography, also have some limitations.
Conclusions.
The present study can provide valuable prognostic information in DCM patients in sinus rhythm with mild to moderate LV dysfunction. The principal new finding of the present study is that the assessment of ME is a powerful independent prognostic index. An ME <11% can therefore help identify patients who are at risk for death and may serve to select the optimal time at which heart transplantation should be recommended to patients with DCM in sinus rhythm when there are limited numbers of donor hearts available. However, further investigations of larger numbers of patients are needed before these conclusions can be applied to patients with more severe LV dysfunction.
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References
|
|---|
1. Fuster V, Gersh BJ, Giuliani ER, Tajik AJ, Brandenburg RO, Frye RL. The natural history of idiopathic dilated cardiomyopathy. Am J Cardiol. 1981;47:525–531[CrossRef][Medline]
2. Stevenson LW, Fowler MB, Schroeder JS, Stevenson WG, Dracup KA, Fond V. Poor survival of patients with idiopathic cardiomyopathy considered too well for transplantation. Am J Med. 1987;83:871–876[CrossRef][Medline]
3. Cohn JN, Archibald DG, Ziesche S, et al. Effect of vasodilator therapy on mortality in chronic congestive heart failure. N Engl J Med. 1986;314:1547–1552[Abstract]
4. Keogh AM, Freund J, Baron DW, Hickie JB. Timing of cardiac transplantation in idiopathic dilated cardiomyopathy. Am J Cardiol. 1988;61:418–422[CrossRef][Medline]
5. Heart Muscle Disease GroupPinamonti B, Di Lenarda A, Sinagra G, Camerini F. Restrictive left ventricular filling pattern in dilated cardiomyopathy assessed by Doppler echocardiography: clinical echocardiographic and hemodynamic correlation and prognostic implications. J Am Coll Cardiol. 1993;22:808–815[Abstract]
6. Kass DA, Maughan WL, Guo ZM, Kono A, Sunagawa K, Sagawa K. Comparative influence of load versus inotropic states on indexes of ventricular contractility: experimental and theoretical analysis based on pressure-volume relationships. Circulation. 1987;76:1422–1436[Abstract/Free Full Text]
7. Hasenfuss G, Holubarsch C, Heiss HW, et al. Myocardial energetics in patients with dilated cardiomyopathy. Circulation. 1989;80:51–64[Abstract/Free Full Text]
8. Ishihara H, Yokota M, Sobue T, Saito H. Relation between ventriculoarterial coupling and myocardial energetics in patients with idiopathic dilated cardiomyopathy. J Am Coll Cardiol. 1994;23:406–416[Abstract]
9. Kanda H, Yokota M, Ishihara H, Nagata K, Kato R, Sobue T. A novel inotropic vasodilator, OPC-18790, reduces myocardial oxygen consumption and improves mechanical efficiency with congestive heart failure. Am Heart J. 1996;132:361–368[CrossRef][Medline]
10. Cappola TP, Kass DA, Nelson GS, et al. Allopurinol improves myocardial efficiency in patients with idiopathic dilated cardiomyopathy. Circulation. 2001;104:2407–2411[Abstract/Free Full Text]
11. Clark DM, Plumb VJ, Epstein AE, Kay GN. Hemodynamic effects of irregular sequence of ventricular cycle lengths during atrial fibrillation. J Am Coll Cardiol. 1997;30:1039–1045[Abstract]
12. Dries DL, Exner DV, Gersh BJ, Domanski MJ, Waclawiw MA, Stevenson LW. Atrial fibrillation is associated with an increased risk for mortality and heart failure progression in patients with asymptomatic and symptomatic left ventricular systolic dysfunction: a retrospective analysis of the SOLVD trials. J Am Coll Cardiol. 1998;32:695–703[Abstract/Free Full Text]
13. Carson PE, Johnson GR, Dunkman WB, Fletcher RD, Farrel L, Cohn JN. The influence of atrial fibrillation on prognosis in mild to moderate heart failure. The V-HeFT studies. Circulation. 1993;(Suppl VI):102–110
14. Richardson P, McKenna W, Bristow M, et al. Report of the 1995 WHO/ISFC Task Force on the definition and classification of cardiomyopathies. Circulation. 1996;93:841–842[Free Full Text]
15. Suga H. Total mechanical energy of a ventricle model and cardiac oxygen consumption. Am J Physiol. 1979;236:H498–505
16. Gibbs CL. Cardiac energetics. Physiol Rev. 1978;58:174–254[Free Full Text]
17. Ganz W, Tamura K, Marcus HS, Donoso R, Yoshida S, Swan HJC. Measurements of coronary sinus blood flow by continuous thermodilution in man. Circulation. 1971;4:181–195
18. Izawa H, Yokota M, Takeichi Y, et al. Adrenergic control of the force-frequency and relaxation-frequency relations in patients with hypertrophic cardiomyopathy. Circulation. 1997;96:2959–2968[Abstract/Free Full Text]
19. Inagaki M, Yokota M, Izawa H, et al. Impaired force-frequency relations in patients with hypertensive left ventricular hypertrophy: a possible marker of the transition from physiological to pathological hypertrophy. Circulation. 1999;99:1822–1830[Abstract/Free Full Text]
20. Kato R, Yokota M, Ishihara H, Sobue T. Correlation between left ventricular contractility and relaxation in patients with idiopathic cardiomyopathy. Clin Cardiol. 1996;19:413–418[Medline]
21. Bing RJ, Hammonad MM, Handelsman JC, et al. The measurement of coronary blood flow, oxygen consumption, and efficiency of the left ventricle in man. Am Heart J. 1949;38:1–24[CrossRef][Medline]
22. Beanlands RS, Bach DS, Raylman R, et al. Acute effects of dobutamine on myocardial oxygen consumption and cardiac efficiency measured using carbon-11 acetate kinetics with dilated cardiomyopathy. J Am Coll Cardiol. 1993;22:1389–1398[Abstract]
23. Wilson JR, Schwartz JS, Sutton MSJ, et al. Prognosis in severe heart failure: relation to hemodynamic measurements and ventricular ectopic activity. J Am Coll Cardiol. 1983;2:403–410[Medline]
24. Kelly TL, Cremo R, Nielsen C, Shabetai R. Prediction of outcome in late-stage cardiomyopathy. Am Heart J. 1990;119:1111–1121[CrossRef][Medline]
25. Kolias TJ, Aaronson KD, Armstrong WF. Doppler-derived dP/dt and –dP/dt predict survival in congestive heart failure. J Am Coll Cardiol. 2000;36:1594–1599[Abstract/Free Full Text]
26. Meeuw LTA, Hess OM, Nonogi H, Monrad ES, Leskosek B, Krayenbuehl HP. Left ventricular volume determination in dogs: a comparison between conductance technique and angiocardiography. Eur Heart J. 1988;9:1018–1026[Abstract/Free Full Text]
27. Applegate RJ, Cheng CP, Little WC. Simultaneous conductance catheter and dimension assessment of left ventricle in intact animals. Circulation. 1990;81:638–648[Abstract/Free Full Text]
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Abstract
Methods