Joost Doornbos

Diastolic Dysfunction in Hypertensive Heart Disease Is Associated With Altered Myocardial Metabolism

BACKGROUND Hypertension is an important clinical problem and is often accompanied by left ventricular (LV) hypertrophy and dysfunction. Whether the myocardial high-energy phosphate (HEP) metabolism is altered in human hypertensive heart disease and whether this is associated with LV dysfunction is not known. METHODS AND RESULTS Eleven patients with hypertension and 13 age-matched healthy subjects were studied with magnetic resonance imaging at rest and with phosphorus-31 magnetic resonance spectroscopy at rest and during high-dose atropine-dobutamine stress. Hypertensive patients showed higher LV mass (98+/-28 g/m2) than healthy control subjects (73+/-13 g/m2, P<0.01). LV filling was impaired in patients, reflected by a decreased peak rate of wall thinning (PRWThn), E/A ratio, early peak filling rate, and early deceleration peak (all P<0. 05), whereas systolic function was still normal. The myocardial phosphocreatine (PCr)/ATP ratio determined in patients at rest (1. 20+/-0.18) and during stress (0.95+/-0.25) was lower than corresponding values obtained from healthy control subjects at rest (1.39+/-0.17, P<0.05) and during stress (1.16+/-0.18, P<0.05). The PCr/ATP ratio correlated significantly with PRWThn (r=-0.55, P<0.01), early deceleration peak (r=-0.56, P<0.01), and with the rate-pressure product (r=-0.53, P<0.001). CONCLUSIONS Myocardial HEP metabolism is altered in patients with hypertensive heart disease. In addition, there is an association between impaired LV diastolic function and altered myocardial HEP metabolism in humans. The level of myocardial PCr/ATP is most likely determined by the level of cardiac work load.

Magnetic resonance measurement of velocity and flow: Technique, validation, and cardiovascular applications

With a newly developed magnetic resonance (MR) technique for blood flow measurements, qualitative and quantitative information on both flow volume and flow velocity in the great vessels can be obtained. MR flow quantitation is performed with a gradient-echo MR sequence with high temporal resolution enabling measurements at frequent intervals throughout the cardiac cycle. MR flow quantitation uses the phase rather than the amplitude of the MR signal to reconstruct the images. These images, often referred to as MR velocity maps or velocity-encoded cine MR images, are two-dimensional displays of flow velocity. From these velocity maps, velocity and volume flow data can be obtained. Previous validation experiments have demonstrated the accuracy of MR velocity mapping, and this technique is now being applied successfully in several clinical fields. MR velocity mapping may be of considerable value when Doppler echocardiography results are unsatisfactory or equivocal, particularly because MR is suited for the analysis of volumetric flow and complex flow patterns. Among the vastly growing number of clinical cardiovascular applications that have been reported are the great arteries and veins, coronary vessels, valvular disease, and the abdominal and peripheral vessels. These items are reviewed, and some aspects of the technique that need improvement are discussed.

Value of Fast Gradient Echo Magnetic Resonance Angiography as an Adjunct to Coronary Arteriography in Detecting and Confirming the Course of Clinically Significant Coronary Artery Anomalies

We investigated the additional value of magnetic resonance (MR) angiography in 12 patients with clinically significant coronary anomalies. In 5 patients, the referring cardiologist requested additional evaluation because coronary arteriography was inconclusive about the course of the anomaly. For comparison, 7 patients with known anomalous coronary arteries were collected from our database. In these patients, there had been no doubt about the course of the anomalous coronary arteries. MR angiography provided the diagnosis in all 5 patients in whom the diagnosis was inconclusive beforehand. From the 7 patients in whom diagnosis had been established previously by contrast arteriography, the anomaly was confirmed in 5 by MR angiography. In 1 patient, the initial diagnosis at contrast arteriography had to be changed as a result of MR angiography. In 1 patient, the MR image was of insufficient quality to be conclusive. In conclusion, in patients with angiographically suspected coronary anomalies, fast gradient echo MR angiography is a helpful adjunct to coronary arteriography in identifying and confirming the origin and course of clinically significant coronary anomalies. The additional value of fast gradient echo MR coronary angiography is the visualization of both the artery and its surrounding structures.

Diffusion-weighted MRI in the characterization of soft-tissue tumors

To explore the potential of perfusion‐corrected diffusion‐weighted magnetic resonance imaging (MRI) in characterizing soft‐tissue tumors.

Postoperative pulmonary flow dynamics after fontan surgery: Assessment with nuclear magnetic resonance velocity mapping

OBJECTIVES This study was performed to assess the value of nuclear magnetic resonance (NMR) velocity mapping for the measurement of pulmonary blood flow after Fontan surgery. BACKGROUND Echocardiographic studies of pulmonary flow after Fontan surgery are not always satisfactory. The newly developed technique of NMR velocity mapping may contribute to the elucidation of the Fontan circulation. METHODS At frequent intervals during the cardiac cycle, forward and backward flow volumes in the pulmonary arteries of nine volunteers were measured, summed and compared with right ventricular stroke volume to validate the velocity mapping technique. In 14 patients after Fontan surgery, assessment of pulmonary flow volumes enabled the evaluation of atriopulmonary and atrioventricular (AV) Fontan connections. The findings were correlated with precordial echocardiography. RESULTS Validation of the NMR technique, obtained from volunteer experiments, showed a high correlation (r = 0.97) between right ventricular stroke volume and volumetric pulmonary stroke flow. In all patients with an atriopulmonary Fontan connection (n = 8), forward flow in the pulmonary artery was biphasic, similar to normal venous flow. Monophasic systolic pulmonary flow curves indicating right ventricle-dependent pulmonary blood flow were found in three of six patients with an AV Fontan connection. In the remaining three patients, the pulmonary flow pattern did not reflect right ventricular contraction. Measurement of flow velocity alone may give a false impression of forward flow and thus of right ventricular contribution. Pulmonary regurgitation was demonstrated in six of eight patients with an atriopulmonary connection. CONCLUSIONS Nuclear magnetic resonance velocity mapping provides accurate and valuable information on pulmonary flow volume and velocity after Fontan surgery. The success of AV Fontan surgery can be deduced from the presence of a monophasic systolic pulmonary flow pattern as demonstrated by NMR velocity mapping. With NMR flow volume analysis, substantial pulmonary regurgitation occurring after atriopulmonary Fontan surgery can be measured.

Mitral valve and tricuspid valve blood flow: Accurate quantification with 3D velocity-encoded MR imaging with retrospective valve tracking

PURPOSE To validate flow assessment performed with three-dimensional (3D) three-directional velocity-encoded (VE) magnetic resonance (MR) imaging with retrospective valve tracking and to compare this modality with conventional two-dimensional (2D) one-directional VE MR imaging in healthy subjects and patients with regurgitation. MATERIALS AND METHODS Patients and volunteers gave informed consent, and local medical ethics committee approval was obtained. Patient data were selected retrospectively and randomly from a database of MR studies obtained between July 2006 and July 2007. The 3D three-directional VE MR images were first validated in vitro and compared with 2D one-directional VE MR images. Mitral valve (MV) and tricuspid valve (TV) flow were assessed in 10 volunteers without valve insufficiency and 20 patients with valve insufficiency, with aortic systolic stroke volume (ASSV) as the reference standard. RESULTS Phantom validation showed less than 5% error for both techniques. In volunteers, 3D three-directional VE MR images showed no bias for MV or TV flow when compared with ASSV, whereas 2D one-directional VE MR images showed significant bias for MV flow (15% overestimation, P < .01). TV flow showed 25% overestimation; however, this was insignificant because of the high standard deviation. Correlation with ASSV was strong for 3D three-directional VE MR imaging (r = 0.96, P < .01 for MV flow; r = 0.88, P < .01 for TV flow) and between MV and TV flow (r = 0.91, P < .01); however, correlation was weaker for 2D one-directional VE MR imaging (r = 0.80, P < .01 for MV flow; r = 0.22, P = .55 for TV flow) and between MV flow and TV flow (r = 0.34, P = .34). In patients (mean regurgitation fractions of 13% and 10% for MV flow and TV flow, respectively), correlation between MV flow and TV flow for 3D three-directional VE MR imaging was strong (r = 0.97, P < .01). CONCLUSION Use of 3D three-directional VE MR imaging enables accurate MV and TV flow quantification, even in patients with valve regurgitation.

Echo planar MRI of the heart on a standard system : Validation of measurements of left ventricular function and mass

OBJECTIVE Our goal was to validate cardiac measurements derived from multishot echo planar MRI (EPI) as compared with the well validated conventional GRE technique. METHOD Ten healthy subjects underwent breath-hold EPI and non-breath-hold GRE imaging in the short axis orientation of the left ventricle (LV) on a standard 1.5 T MR system. Ten section levels were obtained to encompass the entire LV. Measurements were obtained of end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), LV mass, time to end-systole (TES), and peak filling rate (PFR). Analysis of variance was performed to determine agreement between GRE- and EPI-derived measurements. RESULTS The acquisition time for EPI was much shorter than that for GRE (2.5 vs. 15 min). Both imaging techniques yielded good quality images allowing LV volumetrics. Agreement between GRE and EPI was best for measurements of EDV, SV, and LV mass; somewhat less agreement was found for ESV, EF, TES, and PFR. The intraobserver variability for measuring TES and PFR was higher for GRE than EPI (one sided F test; critical values at p = 0.05 were > 3.18). CONCLUSION Multishot EPI of the heart provides accurate measurements of LV function and mass in a time-efficient manner.

Magnetic Resonance Assessment of Aortic Pulse Wave Velocity, Aortic Distensibility, and Cardiac Function in Uncomplicated Type 2 Diabetes Mellitus

BACKGROUND Type 2 diabetes mellitus (DM2) may augment arterial stiffening and thereby modulates left ventricular (LV) function. Cardiovascular magnetic resonance (CMR) is well suited to assess aortic pulse wave velocity (PWV) and aortic distensibility, both markers of arterial stiffness, without the use of geometric assumptions. Furthermore, CMR is a reliable method for assessing left ventricular (LV) function. The purpose of this study was to assess LV function, PWV, and aortic distensibility in patients with DM2 using MR. METHODS Fourteen patients with well controlled, uncomplicated DM2, and 16 age and gender matched healthy subjects were included. PWV was calculated based on MR velocity mapping at two predefined aortic locations. Aortic distensibility was measured in the mid ascending aorta. LV volumes were measured by fast gradient-echo imaging to assess systolic function. Furthermore, mitral inflow was measured by MR velocity mapping to assess diastolic LV function. RESULTS Mean PWV was higher in patients as compared to healthy subjects (6.83 +/- 1.60 m/s vs. 5.65 +/- 0.75 m/s, p < 0.05). This difference was independent of blood pressure. PWV correlated significantly (p < 0.05) with fasting plasma glucose and insulin levels. Aortic distensibility was lower in patients as compared to healthy subjects (4.50 x 10(- 3)+/- 2.24 x 10(- 3) mmHg(- 1) vs. 7.42 x 10(- 3)+/- 3.34 x 10(- 3) mmHg(- 1), p < 0.05). Distensibility correlated negatively with PWV and positively with LV diastolic function (p < 0.05). CONCLUSION A combined CMR assessment of aortic PWV, aortic distensibility, and heart function reveals abnormal PWV and distensibility in patients with DM2, independent of blood pressure. Furthermore, aortic distensibility correlates with diastolic left ventricular function.

Metabolic Response of Normal Human Myocardium to High-Dose Atropine-Dobutamine Stress Studied by 31P-MRS

BACKGROUND 31P-MRS during cardiac stress may provide (patho)physiological insights into the high-energy phosphate metabolism of the myocardium. Accordingly, the purpose of the present study was to determine the metabolic response of normal human myocardium to severe atropine-dobutamine (A-D) stress. To corroborate the results from the present in vivo study, a 31P-MRS experiment was performed with a moving phantom to simulate respiratory motion. METHODS AND RESULTS The phantom experiment showed no relation (P=.371) between the intensity ratio of two separate phosphate peaks and amplitude of phantom excursions. The phosphocreatine (PCr) and ATP signal strength and the PCr/ATP ratio were determined from the left ventricular wall in 20 healthy subjects (posttest likelihood for coronary artery disease was <2.5%) with 31P-MRS at rest and during high-dose A-D stress (rate-pressure product increased threefold). Stress-induced changes were -21% for PCr (P<.001) and -9% for ATP (P<.05). The average PCr/ATP value at rest was 1.42+/-0.18 and decreased by 14% to 1.22+/-0.20 during stress (P<.001). CONCLUSIONS The phantom experiment shows that the in vivo decrease of myocardial PCr/ATP due to high-dose A-D stress we observed is not a motion artifact. Consequently, this indicates that myocardial high-energy phosphate metabolism of the normal human heart is altered at high workloads.

MRI to Evaluate Left Atrial and Ventricular Reverse Remodeling After Restrictive Mitral Annuloplasty in Dilated Cardiomyopathy

BACKGROUND Data on reverse remodeling of the left atrium (LA) and left ventricle (LV) after restrictive annuloplasty in patients with dilated cardiomyopathy are scarce, and follow-up studies are performed with echocardiography. METHODS AND RESULTS Twenty patients with dilated cardiomyopathy and severe mitral regurgitation selected for restrictive mitral annuloplasty underwent serial MRI studies (within 1 week before surgery, and 2 months [n =18] and 1 year [n =13] after surgery). Early mortality was 10%; all patients were free from endocarditis and thromboembolism. New York Heart Association class improved from 3.2+/-0.4 to 1.2+/-0.9. Only 1 patient developed recurrent severe mitral regurgitation during follow-up and it was re-repaired. LA end-systolic volumes decreased significantly over time (from 165+/-48 mL to 109+/-23 mL to 111+/-28 mL; P < 0.01), as did LA end-diastolic volumes (from 92+/-32 mL to 71+/-22 mL to 75+/-17 mL; P = 0.01). LV end-diastolic volumes decreased significantly (from 244+/-56 mL to 184+/-54 mL to 195+/-67 mL; P < 0.01), whereas end-systolic volumes did not change significantly. LV ejection fraction increased significantly (from 35+/-8% to 46+/-13% to 46+/-15%; P < 0.01) and LV mass decreased significantly (from 150+/-43 grams to 132+/-39 grams to 136+/-33 grams; P = 0.02). CONCLUSIONS Restrictive annuloplasty in patients with dilated cardiomyopathy yielded excellent clinical results associated with significant LA and LV reverse remodeling over time as demonstrated by MRI.