Ann Thorac Surg 2000;70:2149-2151
© 2000 The Society of Thoracic Surgeons
Case report
Doppler tissue imaging to predict myocardial recovery during mechanical circulatory support
Emmanuelle Vermes, MDa,
Rémi Houël, MDa,
Marc Simon, MDa,
Paul Le Besnerais, MDa,
Daniel Loisance, MDa
a Service de Chirurgie Thoracique et Cardiovasculaire, CNRS UPRES-A 7054, Association Claude Bernard, Hôpital Henri Mondor, Créteil, France
Accepted for publication March 15, 2000.
Address reprint requests to Dr Loisance, Service de Chirurgie Thoracique et Cardiovasculaire, Hôpital Henri Mondor, 51, avenue du Maréchal de Lattre de Tassigny, 94010 Créteil, France
e-mail: loisance{at}univ-oaris12.fr
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Abstract
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Bridge to recovery is a possibility for patients receiving mechanical circulatory support. However, no reliable factors exist to predict a sustained myocardial recovery. We report the use of a new technique of Doppler tissue imaging to document myocardial recovery in two cases with promising results.
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Introduction
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In patients under mechanical circulatory support (MCS), echocardiography is a useful tool to assess left ventricular (LV) function to detect clues of myocardial recovery. However, no accurate echocardiographic measurements of LV function have proved to be reliable and predictive of a sustained myocardial recovery. Doppler tissue imaging (DTI) is a new imaging method that records velocity of tissue motion within the myocardium [1]. The potential clinical applications of DTI have been evaluated during in vitro and in vivo studies [2], and it appears to be a promising technique that may allow quantitative assessment of regional LV function [3]. The following two observations suggest that DTI could be a reliable tool to assess LV function and determine candidates with the best chance of recovery.
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Case reports
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Case 1
A 13-year-old girl, with a familial history of hypertrophic cardiomyopathy, was admitted in cardiogenic shock after cardiac arrest and cardiopulmonary rescussitation. On admission, she was on ventilatory support and pharmacological support using dobutamine and adrenaline. Transthoracic echocardiogram revealed normal left and right ventricle size and thickness but a severe global hypokinesia. Coronary angiography was normal. Despite pharmacological support, mean arterial pressure was 60 mm Hg and cardiac index was 1.9 L/min/m2 with no diuresis. A biventricular external assist device (Thoratec Inc, Berkeley, CA) implantation was undertaken. Histologic examination of intraoperative myocardial biopsy showed a mild to moderate inflammatory infiltrate and some interstitial edema. On the second and eighth postoperative days, transoesophageal echocardiography was performed using a multiplane probe and available ultrasound system equipped with DTI capabilities (Acuson Sequoia, Mountain View, CA).
Simultaneous acquisition of conventional two-dimensional echocardiographic images and color M-mode tissue Doppler velocities images were recorded (Fig 1) and transferred to a personal computer for off-line processing. Peak endocardial systolic velocities (EV) of LV anterior wall and transmyocardial systolic velocity gradient (MVG) were determined by analyzing the Doppler shift from the color images using a dedicated software environment for vision application (Visilog; Noesis, Paris, France). MVG was defined as the slope of the regression line for the transmural velocity profile between the endocardium and the epicardium across the myocardial wall, as described by Shimizu and associates [4]. EV increased from the second to the eight day (2 to 5 cm/s), with a concomitant increased of fractional shortening (15% to 35%). On the eight postimplantation day, EV and MVG were measured at different pump flow values on a fixed rate mode. Tissue Doppler images were recorded 5 minutes after pump flow was changed. As pump flow was decreased (from 4.5 to 2.5 L/min), MVG and EV increased inversely (from 1.3 to 4 /s and 5 to 8 cm/s, respectively) (Fig 2). These changes occurred while heart rate and mean arterial pressure remained constant. In mean time, M-Mode echocardiography revealed a normal LV function with a consistent aortic valve opening. On the 15th postoperative day, the patient was brought back to the operating room for device removal. Transoesophageal echocardiography was performed before and after assist device removal to further document LV function. Before explantation, MVG and EV were, respectively, 1.2 /s and 1.3 cm/s. Forty minutes after removal, MVG remained low (1.3 /s) while fractional shortening remained within a normal range (30%). On the 26th day after device removal, MVG and EV were, respectively, 3.2 /s and 9 cm/s, showing further normalization of MVG. Transthoracic echocardiography confirmed a normal right and left ejection fraction without myocardial hypertrophy. One month later, she returned home.
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Fig 1. Example of color M-mode images of anterior wall obtained in the transgastric view (0°) with pump flow at 2.5 L/min. The color bar on the left side of the image shows the range of velocity in cm/s. The left ventricular wall is displayed alternatively in red and blue as it moves towards and away, respectively, from the tranducer. Velocity gradient was defined as the slope of linear regression of the myocardial velocity between endocardium (End) and epicardium (Epi).
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Fig 2. Changes in MVG (/s) and EV (cm/s) during pump flow changes for both patients. Increasing in MVG and EV occurs while pump flow is decreased in patient 1. In contrast, MVG and EV remain unchanged in patient 2. (EV = peak endocardial systolic velocity; LV = left ventricular; MVG = transmyocardial systolic velocity gradient.)
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Case 2
A 39-year-old man, with a past medical history of nonischemic heart failure diagnosed in 1992, experienced subsequent recent decompensation and was indicated for a heart transplantation. While he was waiting for a donor, he was readmitted for a further decompensation of end-stage cardiac failure. On admission, echocardiography revealed a dilated cardiomyopathy with a LV end-diastolic diameter of 92 mm and severe global hypokinesia. Mean arterial pressure was 70 mm Hg, and cardiac index was 1.8 L/min/m2. The patient remained anuric with mild liver dysfunction. A biventricular external assist device (Thoratec Inc, Berkeley, CA) was implanted. On the 26th postoperative day, a transoesophageal echocardiography was performed. LV anterior wall EV and MVG were measured at different pump flow set values (6.3 to 3.8 L/min) as described in case 1. No significant EV and MVG changes occurred while pump flow was decreased (Fig 2). M-mode echocardiography revealed persistent global hypokinesia. Heart rate and mean arterial pressure were not significantly changed until pump flow was set at 3.8 L/min. Three months later, this patient is currently waiting for heart transplantation.
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Comment
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LV myocardial recovery in patients under MCS occurs in a limited number of patients. To assess LV recovery, various parameters are used, such as hemodynamic measurement [5], echocardiographic measurement of LV function using shortening fraction, or flow velocity analysis at the tip of the mitral valve [6].
However, none of these parameters seems to be predictive of a sustained myocardial recovery under MCS. Out of five explanted patients reported by Mancini and associates [5], 2 patients died within the first year of ventricular assist device removal and 2 others needed implantation of another assist device. We recently reported two cases of echocardiographic documented recovery after acute myocarditis [7]. Despite maintained improved LV function at the time of device removal, 1 of the 2 patients deteriorated shortly after explantation and necessitated urgent heart transplantation.
DTI is a new echocardiographic method based on the Doppler principle, which allows quantification of transmural myocardial velocities and MVG [1, 2]. Gorcsan and associates [3] have established, in an open chest dog model, that peak endocardial velocity increases with increased intravenous dobutamine doses and correlated significantly with maximal elastance from the pressure-volume relationship. MVG is a new ultrasound index of myocardial function that is independent of the translation motion [8] and remains substantially unchanged by increased preload in early diastole [4]. We established that quantitative assessment of EV and MVG by DTI technique with transoesophageal echocardiography is feasible and of clinical relevance for quantitative echocardiographic evaluation of LV function to document myocardial recovery. Our observations suggest that EV and MVG increase when pump flow is decreased in the presence of complete LV recovery, whereas this changes in MVG does not appear in the absence of myocardial recovery.
Measurement of EV and MVG in patients under MCS could be a baseline for subsequent DTI clinical studies on the myocardial recovery process and to monitor LV function.
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References
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Abstract
Introduction
