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      Assessment of left ventricular preload by cardiac magnetic resonance imaging predicts exercise capacity in adult operated tetralogy of Fallot: a retrospective study

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          Abstract

          Background

          The optimal timing of pulmonary homograft valve replacement (PVR) is uncertain. Cardiopulmonary exercise testing (CPET) and cardiac magnetic resonance (CMR) are often used to guide the clinical decision for PVR in operated tetralogy of Fallot (TOF) patients with significant pulmonary regurgitation (PR). We aim to study the relationship between exercise capacity and CMR in these patients.

          Methods

          The study is a single-centre retrospective analysis of 36 operated TOF patients [median 21.4 (interquartile range 16.4, 26.4) years post-repair; 30 NYHA I, 6 NYHA II; median age 25.2 (interquartile range 19.5-31.7) years, 29 males] with significant PR on CMR who underwent CPET within 15 [median 2.0 (interquartile range 0.8-7.2)] months from CMR. CPET parameters were compared with 30 age- and sex-matched healthy controls [median age 27.8 (interquartile range 21.0-32.8) years; 24 males].

          Results

          Peak systolic blood pressure (177 versus 192 mmHg, p = 0.007), Mets (7.3 versus 9.9, p < 0.001), peak oxygen consumption (VO 2max) (29.2 versus 34.5 ml/kg/min, p < 0.001) and peak oxygen pulse (11.0 versus 13.7 ml/beat, p = 0.003) were significantly lower in TOF group versus control. Univariate analyses showed negative correlation between PR fraction and anaerobic threshold. There was a positive correlation between indexed left (LV) and right (RV) ventricular end-diastolic volumes, as well as indexed LV and effective RV stroke volumes, on CMR and VO 2max and Mets achieved on CPET. These remained significant after adjustment for age and sex.

          Conclusions

          TOF subjects have near normal exercise capacity but significantly lower Mets, VO 2max and peak oygen pulse achieved compared to controls. Increased PR fraction in TOF subjects was associated with lower anaerobic threshold. Higher indexed effective RV stroke volume, a measure of LV preload, was associated with higher VO 2max and Mets achieved, and may potentially be used as a predictor of exercise capacity.

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          Most cited references21

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          ESC Guidelines for the management of grown-up congenital heart disease (new version 2010).

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            Long-term outcome in patients undergoing surgical repair of tetralogy of Fallot.

            Although corrective surgery for tetralogy of Fallot has been available for more than 30 years, the occurrence of late sudden death in patients in whom surgery was apparently successful remains worrisome. We studied long-term survival among 163 patients who survived 30 days after complete repair of tetralogy of Fallot, examining follow-up hospital records and death certificates when relevant. The overall 32-year actuarial survival rate among all patients who survived surgery was 86 percent, as compared with an expected rate of 96 percent in a control population matched for age and sex (P < 0.01). Thirty-year actuarial survival rates were calculated for the patient subgroups. The survival rates among patients less than 5 years old, 5 to 7 years old, and 8 to 11 years old were 90, 93, and 91 percent, respectively--slightly less than the expected rates (P < 0.001, P = 0.06, and P = 0.02). Among patients 12 years old or older at the time of surgery, the survival rate was 76 percent, as compared with an expected rate of 93 percent (P < 0.001). The performance of a palliative Blalock-Taussig shunt procedure before repair, unlike the performance of a Waterston or Potts shunt procedure, was not associated with reduced long-term survival, nor was the need for a trans-annular patch at the time of surgery. Independent predictors of long-term survival were older age at operation (P = 0.02) and a higher ratio of right ventricular to left ventricular systolic pressure after surgery (P = 0.008). Late sudden death from cardiac causes occurred in 10 patients during the 32-year period. Among patients with surgically repaired tetralogy of Fallot, the rate of long-term survival after the postoperative period is excellent but remains lower than that in the general population. The risk of late sudden death is small.
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              Preoperative thresholds for pulmonary valve replacement in patients with corrected tetralogy of Fallot using cardiovascular magnetic resonance.

              To facilitate the optimal timing of pulmonary valve replacement, we analyzed preoperative thresholds of right ventricular (RV) volumes above which no decrease or normalization of RV size takes place after surgery. Between 1993 and 2006, 71 adult patients with corrected tetralogy of Fallot underwent pulmonary valve replacement in a nationwide, prospective follow-up study. Patients were evaluated with cardiovascular magnetic resonance both preoperatively and postoperatively. Changes in RV volumes were expressed as relative change from baseline. RV volumes decreased with a mean of 28%. RV ejection fraction did not change significantly after surgery (from 42+/-10% to 43+/-10%; P=0.34). Concomitant RV outflow tract reduction resulted in a 25% larger decrease of RV volumes. After correction for surgical RV outflow tract reduction, higher preoperative RV volumes (mL/m2) were independently associated with a larger decrease of RV volumes (RV end-diastolic volume: beta=0.41; P<0.001). Receiver operating characteristic analysis revealed a cutoff value of 160 mL/m2 for normalization of RV end-diastolic volume or 82 mL/m2 for RV end-systolic volume. Overall, we could not find a threshold above which RV volumes did not decrease after surgery. Preoperative RV volumes were independently associated with RV remodeling and also when corrected for a surgical reduction of the RV outflow tract. However, normalization could be achieved when preoperative RV end-diastolic volume was <160 mL/m2 or RV end-systolic volume was <82 mL/m2.
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                Author and article information

                Contributors
                jonyap@yahoo.com
                tan.ju.le@nhcs.com.sg
                le.thu.thao@nhcs.com.sg
                gao.fei@nhcs.com.sg
                zhong.liang@nhcs.com.sg
                reginald.liew@gmail.com
                tan.swee.yaw@nhcs.com.sg
                tan.ru.san@nhcs.com.sg
                Journal
                BMC Cardiovasc Disord
                BMC Cardiovasc Disord
                BMC Cardiovascular Disorders
                BioMed Central (London )
                1471-2261
                23 September 2014
                23 September 2014
                2014
                : 14
                : 1
                : 122
                Affiliations
                [ ]Department of Cardiology, National Heart Centre Singapore, 5 Hospital Drive, Singapore, 169609 Singapore
                [ ]Duke-NUS Graduate Medical School, Singapore, 8 College Rd, Singapore, 169857 Singapore
                Article
                768
                10.1186/1471-2261-14-122
                4177590
                25245139
                3c301c3e-48b5-42e3-a7f3-2a4ab5460320
                © Yap et al.; licensee BioMed Central Ltd. 2014

                This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

                History
                : 16 March 2014
                : 16 September 2014
                Categories
                Research Article
                Custom metadata
                © The Author(s) 2014

                Cardiovascular Medicine
                exercise capacity,cardiac magnetic resonance imaging,tetralogy of fallot

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