Europace Advance Access originally published online on January 28, 2008
Europace 2008 10(3):379-383; doi:10.1093/europace/eum297
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RESYNCHRONISATION THERAPY
Chronic cardiac resynchronization therapy reverses cardiac remodelling and improves invasive haemodynamics of patients with severe heart failure on optimal medical treatment
Department of Internal Medicine, Division of Cardio-Vascular Medicine, Kurume University School of Medicine, 67 Asahi-machi, Kurume 830-0011, Japan
Manuscript submitted 18 June 2007. Accepted after revision 18 December 2007.
* Corresponding author. Tel: +81 942 31 7562; fax: +81 942 33 6509. E-mail address: teruhisa{at}med.kurume-u.ac.jp
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Abstract |
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Aims: The aim of this study was to assess chronic invasive haemodynamic effects of cardiac resynchronization therapy (CRT) in patients with severe heart failure.
Methods and results: Seventeen patients with New York Heart Association (NYHA) class III or IV and QRS duration >120 ms on optimal treatments underwent CRT. Haemodynamic data were obtained by cardiac catheterization before and 1 month after CRT. Clinical parameters and exercise tolerance were also evaluated. Chronic CRT improved haemodynamics significantly; mean pulmonary capillary wedge pressure decreased from 15.9 ± 6.1 to 10.2 ± 5.3 mmHg (P < 0.05), systolic pulmonary artery pressure decreased from 36.5 ± 13.2 to 26.7 ± 11.9 mmHg (P < 0.05), left ventricular end-diastolic pressure decreased from 15.6 ± 7.2 to 10.5 ± 7.3 mmHg (P < 0.05), end-diastolic volume decreased from 358.8 ± 84.6 to 322.9 ± 99.0 mL (P < 0.05), end-systolic volume decreased from 264.1 ± 67.6 to 219.2 ± 74.3 mL (P < 0.05), left ventricular ejection fraction increased from 25.4 ± 6.2 to 33.1 ± 4.9% (P < 0.05), and cardiac index increased from 1.9 ± 0.4 to 2.2 ± 0.5 L/min/m2 (P < 0.05). Chronic CRT significantly improved functional capacity such as NYHA classification, 6 min walk distance, and peak oxygen uptake.
Conclusion: Chronic CRT improved not only symptoms and exercise tolerance but also invasive haemodynamics associated with reversed cardiac remodelling.
Key Words: Resynchronization, Haemodynamic effect, Cardiac catheterization, Reverse cardiac remodelling
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Introduction |
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Intraventricular conduction delay commonly occurs in patients with chronic heart failure and produces dyssynchronous ventricular contraction that further impairs cardiac function.1
–3 An overwhelming amount of evidence from prospective randomized controlled trials supports the clinical efficacy and safety of cardiac resynchronization therapy (CRT) in patients with moderate or severe heart failure and ventricular dyssynchrony. CRT has been demonstrated to decrease hospitalization and mortality and to improve symptoms, exercise tolerance, and quality of life.4–10 CRT also has been demonstrated to improve long-term cardiac function assessed by echocardiography.11–13 However, it is well known that the echocardiographic assessment of cardiac function may not be so accurate in the presence of segmental wall motion abnormality.14 Moreover, reports of the chronic effects of CRT on invasive haemodynamics have been few. Accordingly, we assessed the chronic haemodynamic effects of CRT by cardiac catheterization in patients with severe heart failure on optimal medical treatment. |
Methods |
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Patients
The entry criteria included New York Heart Association (NYHA) functional class III or IV heart failure and QRS complex duration >120 ms, despite optimal pharmacological therapy in the stable condition for at least 1 month. The drugs prescribed for them were angiotensin-converting enzyme-inhibitor, angiotensin receptor blocker, diuretics, digitalis, and/or β-blocker (Table 1). Patients were excluded from the study if they had any of following: unstable angina, acute myocardial infarction, coronary artery revascularization within 3 months before enrolment, treatment with intravenous inotropic agents, or correctable valvular disease. Patients were admitted to our ward to receive optimal medical treatment. When the condition of patients was stable for at least 1 month and no further improvement was obtained with medical treatments, they underwent CRT. In 17 patients, haemodynamic data were obtained before and 1 month after CRT by cardiac catheterization. The pharmacological therapy was not changed in order to evaluate the effect of CRT. Written informed consent was obtained from all patients. The study protocol was approved by the Ethics Committee of human investigations at our institution.
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Catheterization protocol and pacemaker implantation procedure
Haemodynamic data were obtained during cardiac catheterization before and 1 month after CRT. Patients were examined while in a supine, non-sedative state. A thermodilution Swan–Ganz catheter (Edwards Lifesciences T173HF6, Irvine, CA, USA) was inserted via the femoral vein and positioned in the pulmonary artery so that mean pulmonary capillary wedge pressure (PCWP) recordings were obtained upon balloon inflation. Cardiac output was recorded in triplicate or until three recordings within 10% of each other were obtained. Systolic pulmonary artery pressure and mean right atrium pressure were also evaluated. Then a 6F pigtail catheter (SPC-454D, Millar Instruments, Houston, TX, USA) was advanced via femoral artery and placed so that the pigtail tip lay at the distal left ventricular apex. Left ventricular end-diastolic pressure (LVEDP), left ventricular ejection fraction (LVEF), end-diastolic volume (EDV), and end-systolic volume (ESV) by cineventriculography were also evaluated. Because three patients had aortic valve replacement, we were not able to insert a catheter into the left ventricle and not able to evaluate LVEDP.
The pacemaker for CRT was the triple-output device (InSync 8040, Medtronic, Minneapolis, MN, USA) in 11 patients. In six patients, a dual-chamber pacemaker (Kappa 731, Medtronic) was implanted with a bipolar Y-adapter (5866-38M, Medtronic) for connecting the right ventricular and left ventricular leads. The left ventricular pacing lead [model 2187 (n = 11) or model 4023 (n = 6), Medtronic] was inserted by transvenous approach through the coronary sinus vein laterally (n = 8) or postero-laterally (n = 7) or antero-laterally (n = 2). The pacemaker device was programmed with the DDD mode of a lower rate limit at 60 bpm. The maximal tracking rate was determined by cardiopulmonary exercise testing before CRT. The atrioventricular interval was adjusted to maximize left ventricular filling time using Doppler echocardiography,15 and no adjustment was made for the interventricular interval. We did not change these pacing modes for the chronic study. Thereafter, their hospitalization was continued for at least 1 month in order to make sure that the same medications were continued and the same daily activity was maintained for the study periods.
Clinical parameters and exercise tolerance
Clinical parameters and exercise tolerance were evaluated before and 1 month after CRT. QRS duration on standard 12-lead ECG, cardiothoracic ratio (CTR) on chest X-ray, and brain natriuretic peptide (BNP) were also obtained. A 6 min walk test was carried out and the total walking distance was determined. For quantitative evaluation for exercise tolerance, cardiopulmonary exercise testing was performed using a bicycle ergometer.16,17 In addition, the peak oxygen uptake (peak VO2) was calculated (Oxycon Alpha, Jaeger, Wurzburg, Germany). Because three patients had severe heart failure with NYHA functional class IV, they were not able to undergo cardiopulmonary exercise testing.
Statistical analysis
Data are presented as mean ± SD. Paired t-tests were performed for comparisons before and after CRT. A value of <0.05 was considered statistically significant.
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Results |
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Table 1 shows the baseline clinical characteristics of enrolled patients. As shown in Table 1, the aetiology of heart failure was various, including dilated cardiomyopathy and corrected valvular heart disease. Two patients had coronary artery disease. Thus, the majority of enrolled patients had non-ischaemic cardiomyopathy. The aetiology of QRS prolongation was also various, including intraventricular conduction disturbance, complete left bundle branch block, complete right bundle branch block, and right ventricular pacing. The mean QRS duration before CRT was 161 ± 37 ms. Although all patients were in NYHA class III (n = 14) or IV (n = 3), they were in stable clinical condition on several kinds of medications. Because six patients did not tolerate β-blockers, they were not on them.
Haemodynamics
Chronic CRT (1 month after CRT) significantly decreased QRS duration from 161 ± 37 to 130 ± 24 ms (P < 0.05, n = 17). Chronic CRT did not change systolic blood pressure (98.2 ± 16.1 mmHg before CRT to 91.8 ± 13.8 mmHg after CRT, NS, n = 17) and heart rate (67.3 ± 8.9 bpm before CRT to 69.6 ± 6.0 bpm after CRT, NS, n = 17) at the time of cardiac catheterization. As shown in Figure 1, chronic CRT not only produced significant decreases in all pressure values (except right atrial pressure) but also reversed cardiac remodelling with increased LVEF and decreased EDV and ESV.
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Clinical parameters and exercise tolerance
Chronic CRT significantly (P < 0.05 for all) improved NYHA classification, decreased CTR on chest X-ray, decreased BNP, increased 6 min walk distance, and increased peak VO2 (Figure 2).
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Discussion
Although the sample size is small, this is the first report which described chronic effects of CRT on invasive haemodynamics with clinical parameters as well as quantitative exercise tolerance measurements. Our study demonstrated that chronic CRT improved invasive haemodynamics (mean PCWP, systolic pulmonary artery pressure, cardiac index, LVEDP, LVEF, EDV, ESV), clinical parameters (NYHA, CTR, BNP), and exercise tolerance (6 min walk distance, peak VO2).
Baseline characteristics and chronic effects
As apparent from the baseline values of LVEF (mean 25.4%), BNP (mean 644 pg/mL), and peak VO2 (mean 12.8 mL/min/kg), the enrolled subjects had severe cardiac dysfunction with decreased exercise tolerance, in spite of optimal medical treatments. Accordingly, we chose CRT as the last treatment. Recently, Steendijk et al.18 have published results of invasive haemodynamic effects of chronic (6 months) CRT. Our results were very similar to those of Steendijk et al.,18 the mean decrease in LVEDP in their study was 5 vs. 5 mmHg in our study, the increase in cardiac output was 0.4 vs. 0.49 L/min, the increase in LVEF was 11 vs. 8%, and the decrease in EDV was 52 vs. 36 mL. Thus, our study not only confirmed the previous results by Steendijk et al.18 but also suggests that chronic haemodynamic improvements and reverse cardiac remodelling occur in as much as 1 month after CRT. Although the improvement of exercise tolerance evaluated by 6 min walk distance was reported, 6 min walk test is somewhat subjective. In this study, we evaluated exercise tolerance with the very quantitative way. Peak VO2 was significantly increased, associated with longer 6 min walk distance and improved NYHA classification status. Thus, our study confirmed the previous reports.16,17
Although there was no control group in our study, we do not think that the improvements reflected the natural course. As stated in the Methods section, the enrolled patients were hospitalized for at least 1 month prior to the study in order to be stable condition. We followed-up them carefully on the same daily activity and same medications in our ward. We studied them at the point when no further improvement was anticipated with optimal medical treatment.
Limitations
As stated often in the earlier discussion, the number of patients was small. We obtained invasive haemodynamics 1 month after CRT, which may have been too short in the clinical point of view. The aetiology of heart failure was heterogeneous. It is possible that chronic haemodynamic responses may differ depending on the aetiology. We studied patients with severe heart failure. It is possible that chronic haemodynamic responses may differ depending on the severity of heart failure. Finally, there was no control group.
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Conclusions |
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Chronic CRT improved symptoms, exercise tolerance, and invasive haemodynamics associated with reversed cardiac remodelling in patients with severe heart failure and conduction delay.
Conflict of interest: none declared.
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References |
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