[Cardiac MRI in the follow-up of adult congenital cardiomyopathy patients]

Magnetic resonance imaging is a rapidly developing modality in cardiology. It offers an excellent image definition and a large field of view, allowing a more accurate morphological assessment of cardiac malformations. Due to its unique versatility and its ability to provide myocardial tissue characterization, cardiac magnetic resonance (CMR) is now recognized as a central imaging modality for a wide range of congenital heart diseases, including assessment of post-surgical cardiac anatomy, quantification of valvular disease and detection of myocardial ischemia. CMR provides useful diagnostic information without any radiation exposure, and improves the global management of patients with congenital heart disease.

Future strategies in the management of coronary artery disease

New diagnostic techniques have now become available that will enable us to obtain information on coronary artery disease (CAD), which was not previously possible. This is urgently needed, since changes in CAD management are highly desirable considering that up to 60% of patients die due to an insufficient diagnostic strategy (reactive strategy). In this article, the pathophysiology of CAD and the evidence of current concepts on coronary atherosclerosis are critically reviewed. Consequently, a shift from a 'reactive strategy' of CAD management to an active strategy is proposed in order to detect and treat patients before acute myocardial infarcts occur. Reliability, repeatability, cost-effectiveness and comfort are important features of an optimal test for this active strategy. This perspective gives an overview of current and future tests with respect to these features. The novel tomographic techniques are particularly promising with respect to standardization and reproducibility, which will set the basis for the determination of test performance and, consequently, cost-effectiveness. Assessment of cost-effectiveness is increasingly important, since prevalence of CAD is high and will most likely increase, while resources will remain restricted in most countries. Considering these economic restrictions, this article also proposes new mathematical tools using data from prospective trials and large international registries as an objective means to select the best tests for CAD diagnosis and management, and to identify those patient subsets which benefit most from an active strategy.

Relation of cardiac troponin I measurements at 24 and 48 hours to magnetic resonance-determined infarct size in patients with ST-elevation myocardial infarction

Levels of circulating cardiac troponin I (cTnI) or T are correlated to extent of myocardial destruction after an acute myocardial infarction. Few studies analyzing this relation have employed a second-generation cTnI assay or cardiac magnetic resonance (CMR) as the imaging end point. In this post hoc study of the Efficacy of FX06 in the Prevention of Mycoardial Reperfusion Injury (F.I.R.E.) trial, we aimed at determining the correlation between single-point cTnI measurements and CMR-estimated infarct size at 5 to 7 days and 4 months after a first-time ST-elevation myocardial infarction (STEMI) and investigating whether cTnI might provide independent prognostic information regarding infarct size at 4 months even taking into account early infarct size. Two hundred twenty-seven patients with a first-time STEMI were included in F.I.R.E. All patients received primary percutaneous coronary intervention within 6 hours from onset of symptoms. cTnI was measured at 24 and 48 hours after admission. CMR was conducted within 1 week of the index event (5 to 7 days) and at 4 months. Pearson correlations (r) for infarct size and cTnI at 24 hours were r = 0.66 (5 days) and r = 0.63 (4 months) and those for cTnI at 48 hours were r = 0.67 (5 days) and r = 0.65 (4 months). In a multiple regression analysis for predicting infarct size at 4 months (n = 141), cTnI and infarct location retained an independent prognostic role even taking into account early infarct size. In conclusion, a single-point cTnI measurement taken early after a first-time STEMI is a useful marker for infarct size and might also supplement early CMR evaluation in prediction of infarct size at 4 months.

Effect of intravenous FX06 as an adjunct to primary percutaneous coronary intervention for acute ST-segment elevation myocardial infarction results of the F.I.R.E. (Efficacy of FX06 in the Prevention of Myocardial Reperfusion Injury) trial

OBJECTIVES

The purpose of this study was to investigate whether FX06 would limit infarct size when given as an adjunct to percutaneous coronary intervention.

BACKGROUND

FX06, a naturally occurring peptide derived from human fibrin, has been shown to reduce myocardial infarct size in animal models by mitigating reperfusion injury.

METHODS

In all, 234 patients presenting with acute ST-segment elevation myocardial infarction were randomized in 26 centers. FX06 or matching placebo was given as intravenous bolus at reperfusion. Infarct size was assessed 5 days after myocardial infarction by late gadolinium enhanced cardiac magnetic resonance imaging. Secondary outcomes included size of necrotic core zone and microvascular obstruction at 5 days, infarct size at 4 months, left ventricular function, troponin I levels, and safety.

RESULTS

There were no baseline differences between groups. On day 5, there was no significant difference in total late gadolinium enhanced zone in the FX06 group compared with placebo (reduction by 21%; p = 0.207). The necrotic core zone, however, was significantly reduced by 58% (median 1.77 g [interquartile range 0.0, 9.09 g] vs. 4.20 g [interquartile range 0.3, 9.93 g]; p < 0.025). There were no significant differences in troponin I levels (at 48 h, -17% in the FX06 group). After 4 months, there were no longer significant differences in scar size. There were numerically fewer serious cardiac events in the FX06-treated group, and no differences in adverse events.

CONCLUSIONS

In this proof-of-concept trial, FX06 reduced the necrotic core zone as one measure of infarct size on magnetic resonance imaging, while total late enhancement was not significantly different between groups. The drug appears safe and well tolerated. (Efficacy of FX06 in the Prevention of Myocardial Reperfusion Injury [F.I.R.E.]; NCT00326976).

How we perform myocardial perfusion with cardiovascular magnetic resonance

Cardiovascular magnetic resonance first-pass perfusion imaging has developed considerably over the past decade. Several studies have shown that this technique is accurate for the detection of myocardial ischemia. In this article we outline the procedure of myocardial perfusion imaging with cardiovascular magnetic resonance as it is performed at our centers, describe the sequences that are currently used in more detail, review our process of image interpretation, and highlight potential pitfalls that we have encountered in our experience with performing this technique in over 2000 patients.

Rationale and Design of the ‘F.I.R.E.’ Study

Immediate reopening of acutely occluded coronary arteries via primary percutaneous coronary intervention (PCI) is the treatment of choice to salvage the ischemic myocardium in the setting of ST-segment elevation myocardial infarction (STEMI). However, the sudden re-initiation of blood flow achieved with PCI can lead to a local acute inflammatory response with further endothelial and myocardial damage. This phenomenon, described as 'reperfusion injury', has been recognized for several decades, yet no pharmacologic intervention has so far succeeded in reducing myocardial damage linked to reperfusion. FX06 is a naturally occurring peptide derived from the neo-N-terminus of fibrin (Bbeta(15-42)). It prevents leukocyte migration through the gap junctions of endothelial cells. Experimental studies have shown that FX06 inhibits the binding of the proinflammatory fibrin E1 fragment to VE-cadherin expressed in the adherence junction. It represents a novel approach to reducing local and systemic inflammation, including myocardial reperfusion injury, in the adherens junction. The present multicenter, double-blind, randomized, placebo-controlled study is designed to test the hypothesis that FX06 injection during and immediately after primary PCI can reduce infarct size in patients with STEMI. The primary outcome measure of efficacy in this study is the degree of myocardial salvage calculated as the difference between the perfusion defect before and after PCI, determined by myocardial perfusion scintigraphy during rest. Further, infarct size at the end of the index hospitalization, as well as at 4 months, will be measured by cardiac magnetic resonance imaging. The present position paper describes the rationale, design and the methods utilized in this trial.

The future of cardiovascular imaging and non-invasive diagnosis☆A joint statement from the European Association of Echocardiography, the Working Groups on Cardiovascular Magnetic Resonance, Computers in Cardiology, and Nuclear Cardiology of the European Society of Cardiology, the European Association of Nuclear Medicine and the Association for European Paediatric Cardiology

Advances in medical imaging now make it possible to investigate any patient with cardiovascular disease using multiple methods which vary widely in their technical requirements, benefits, limitations, and costs. The appropriate use of alternative tests requires their integration into joint clinical diagnostic services where experts in all methods collaborate. This statement summarises the principles that should guide developments in cardiovascular diagnostic services.

The future of cardiovascular imaging and non-invasive diagnosis. A joint statement from the European Association of Echocardiography, the Working Groups on Cardiovascular Magnetic Resonance, Computers in Cardiology, and Nuclear Cardiology, of the European Society of Cardiology, the European Association of Nuclear Medicine and the Association for European Paediatric Cardiology

Advances in medical imaging now make it possible to investigate any patient with cardiovascular disease using multiple methods which vary widely in their technical requirements, benefits, limitations and costs. The appropriate use of alternative tests requires their integration into joint clinical diagnostic services where experts in all methods collaborate. This statement summarises the principles that should guide developments in cardiovascular diagnostic services.

The future of cardiovascular imaging and non-invasive diagnosis: A joint statement from the European Association of Echocardiography, the Working Groups on Cardiovascular Magnetic Resonance, Computers in Cardiology, and Nuclear Cardiology, of the European Society of Cardiology, the European Association of Nuclear Medicine, and the Association for European Paediatric Cardiology

Advances in medical imaging now make it possible to investigate any patient with cardiovascular disease using multiple methods which vary widely in their technical requirements, benefits, limitations, and costs. The appropriate use of alternative tests requires their integration into joint clinical diagnostic services where experts in all methods collaborate. This statement summarizes the principles that should guide developments in cardiovascular diagnostic services.

Detection of coronary artery disease by magnetic resonance myocardial perfusion imaging with various contrast medium doses: first European multi-centre experience

AIMS

Magnetic resonance (MR) first-pass myocardial perfusion imaging during hyperaemia detects coronary artery stenoses in humans with test sensitivity depending on contrast medium (CM)-induced signal change in myocardium. In this prospective multi-centre study, the effect of CM dose on myocardial signal change and on diagnostic performance was evaluated using a stress-only approach.

METHODS AND RESULTS

Ninety-four patients with known or suspected coronary artery disease (CAD) were randomised to 0.05,0.10, or 0.15 mmol/kg body weight of an extravascular CM (Gd-DTPA) and X-ray coronary angiography was performed within 30 days prior/after the MR examination. A multi-slice MR technique with identical hardware and software in all centres was used during hyperaemia (adenosine 0.14 mg/kg/min) to monitor myocardial CM wash-in kinetics and data were analysed semi-automatically in a core laboratory. Protocol violations resulted in 80 complete studies with CAD (defined as > or =1 vessel with diameter stenosis > or =50% on quantitative coronary angiography) present in 19/29, 13/24, and 20/27 patients for doses 1, 2, and 3, respectively. In normal myocardium, the upslope increased with CM dose (overall-p<0.0001, ANOVA). For CAD detection the area under the receiver operator characteristics curve for subendocardial data (3 slices with quality score<4 representing 86% of cases) was 0.91+/-0.07 and 0.86+/-0.08 for doses 2 and 3, respectively, and was lower for dose 1 (0.53+/-0.13, p<0.01 and p<0.02 vs. doses 2 and 3, respectively). Corresponding sensitivities/specificities (95% confidence intervals) for pooled doses 2/3 were 93% (77-99%; ns vs. dose 1) and 75% (48-92%;p<0.05 vs. dose 1), respectively.

CONCLUSIONS

With increasing doses of CM, a higher signal response in the myocardium was achieved and consequently this stress-only protocol, with CM doses of 0.10-0.15 mmol/kg combined with a semi-automatic analysis, yielded a high diagnostic performance for the detection of CAD.

Myocardial first-pass perfusion magnetic resonance imaging: a multicenter dose-ranging study

BACKGROUND

MRI can identify patients with obstructive coronary artery disease by imaging the left ventricular myocardium during a first-pass contrast bolus in the presence and absence of pharmacologically induced myocardial hyperemia. The purpose of this multicenter dose-ranging study was to determine the minimally efficacious dose of gadopentetate dimeglumine injection (Magnevist Injection; Berlex Laboratories) for detecting obstructive coronary artery disease.

METHOD AND RESULTS

A total of 99 patients scheduled for coronary artery catheterization as part of their clinical evaluation were enrolled in this study. Patients were randomized to 1 of 3 doses of gadopentate dimeglumine: 0.05, 0.10, or 0.15 mmol/kg. First-pass perfusion imaging was performed during hyperemia (induced by a 4-minute infusion of adenosine at a rate of 140 microg x kg(-1) x min(-1)) and then again in the absence of adenosine with otherwise identical imaging parameters and the same contrast dose. Perfusion defects were evaluated subjectively by 4 blinded reviewers. Receiver-operating curve analysis showed that the areas under the receiver-operating curve were 0.90, 0.72, and 0.83 for the low-, medium-, and high-contrast doses, respectively, compared with quantitative coronary angiography (diameter stenosis > or =70%). For the low-dose group, mean sensitivity was 93+/-0%, mean specificity was 75+/-7%, and mean accuracy was 85+/-3%.

CONCLUSIONS

First-pass perfusion MRI is a safe and accurate test for identifying patients with obstructive coronary artery disease. A low dose of 0.05 mmol/kg gadopentetate dimeglumine is at least as efficacious as higher doses.

Regional myocardial ischemia in hypertrophic cardiomyopathy: Impact of myectomy

OBJECTIVE

Chest pain is a common finding in patients with hypertrophic cardiomyopathy and can be observed in 40% to 50% of all patients. However, the pathogenesis of these ischemia-like symptoms is still unclear.

METHODS

Twenty-two patients with hypertrophic cardiomyopathy and 15 controls underwent positron emission tomography for evaluation of regional myocardial perfusion and coronary flow reserve (hyperemic/baseline myocardial blood flow). Myocardial perfusion (mL/min/g) was measured using [(13)N]ammonia at rest and during hyperemia with dipyridamole (0.56 mg/kg intravenously). Regional coronary flow reserve was assessed in 3 planes (apical, midventricular, basal) in 4 regions (septal, anterior, lateral, inferior). Patients were divided into 2 groups: group 1 consisted of 11 patients treated with surgical myectomy (age 56 +/- 10 years) and group 2 consisted of 11 patients treated medically (age 53 +/- 13 years).

RESULTS

Mean global coronary flow reserve was 3.87 +/- 0.92 in controls but 2.31 +/- 0.40 in operated (P <.001 vs controls) and 1.76 +/- 0.58 in medically treated patients (P <.001 vs controls, P <.05 vs operated). Similarly, septal coronary flow reserve was 4.19 +/- 1.22 in controls but significantly reduced in operated patients (2.26 +/- 0.48, P <.001 vs controls) and in medically treated patients (1.76 +/- 0.58; P <.001 vs controls). However, septal flow reserve was significantly higher in operated patients than in patients with medically treated hypertrophic cardiomyopathy (+37%, P <.05), mainly due to a reduced resting myocardial perfusion.

CONCLUSIONS

Global and regional myocardial perfusion is reduced in patients with hypertrophic cardiomyopathy. However, myectomy may have a beneficial effect on septal perfusion and flow reserve. Thus, ischemia seems to play an important role in the symptomatology and pathophysiology of hypertrophic cardiomyopathy.

Integration of vascular biology and magnetic resonance imaging in the understanding of atherothrombosis and acute coronary syndromes

The interaction between the vulnerable atherosclerotic plaque prone to disruption and thrombus formation is the cornerstone of acute coronary syndrome (ACS). Although distinct from one another, the atherosclerotic and thrombotic processes appear to be interdependent, hence the term atherothrombosis. Inflammation is a crucial common pathophysiological mechanism. Overall, the association of plaque vulnerability and ACS has been well documented. Given the multifactorial origin of atherothrombosis the best preventive approach should be aggressive management of all the risk factors. New interventions should be directed toward decreasing vulnerability of the lesions thereby decreasing the risk of ACS.

Magnetic resonance myocardial first-pass perfusion imaging: parameter optimization for signal response and cardiac coverage

Fast imaging techniques allow monitoring of contrast medium (CM) first-pass kinetics in a multislice mode. Employing shorter recovery times improves cardiac coverage during first-pass conditions, but potentially flattens signal response in the myocardium. The aim of this study was therefore to compare in patients with suspected coronary artery disease (CAD) two echo-planar imaging strategies yielding either extended cardiac coverage or optimized myocardial signal response (protocol A/B, six/four slices; preparation pulse, 60 degrees /90 degrees; delay time, 10/120 msec; readout flip angle, 10 degrees /50 degrees; respectively). In phantoms and myocardium of normal volunteers (N= 10) the CM-induced signal increase was 2.5-3 times higher with protocol B (P < 0.005) than with protocol A. For the detection of individually diseased coronary arteries (> or =1 stenosis with > or =50% diameter reduction on quantitative coronary angiography (QCA)), receiver-operator characteristics of protocol B (signal upslope in 32 sectors/heart) yielded a sensitivity/specificity of 82%/73%, which was superior to protocol A (P < 0.05, N= 14). For the overall detection of CAD, the sensitivity/specificity of protocol B was 85%/81%. An adequate signal response in the myocardium is crucial for a reliable detection of perfusion deficits during first-pass conditions. The presented protocol B detects CAD with a sensitivity and specificity similar to scintigraphic techniques.

Effect of exercise training on postexercise oxygen uptake kinetics in patients with reduced ventricular function

BACKGROUND

The time required for oxygen uptake (O(2)) to return to baseline level (recovery kinetics) is prolonged in patients with reduced ventricular function, and the degree to which it is prolonged is related to the severity of heart failure, markers of abnormal ventilation, and prognosis. In the present study, we sought to determine the effect of exercise training on O(2) recovery kinetics in patients with reduced ventricular function.

METHODS

Twenty-four male patients with reduced ventricular function after a myocardial infarction were randomized to either a 2-month high-intensity residential exercise training program or to a control group. O(2) kinetics in recovery from maximal exercise were calculated before and after the study period and expressed as the slope of a single exponential relation between O(2) and time during the first 3 min of recovery.

RESULTS

Peak O(2) increased significantly in the exercise group (19.4 +/- 3.0 mL/kg/min vs 25.1 +/- 4.7 mL/kg/min, p < 0.05), whereas no change was observed in control subjects. The O(2) half-time in recovery was reduced slightly after the study period in both groups (108.7 +/- 33.1 to 102.1 +/- 50.5 s in the exercise group and 122.3 +/- 68.7 to 107.5 +/- 36.0 s in the control group); neither the change within or between groups was significant. The degree to which O(2) was prolonged in recovery was inversely related to measures of exercise capacity (peak O(2), watts achieved, and exercise time; r = - 0.48 to - 0.57; p < 0.01) and directly related to the peak ventilatory equivalents for oxygen (r = 0.59, p < 0.01) and carbon dioxide (r = 0.57, p < 0.01).

CONCLUSION

Two months of high-intensity training did not result in a faster recovery of O(2) in patients with reduced ventricular function. This suggests that adaptations to exercise training manifest themselves only during, but not in, recovery from exercise.

Aortic and mitral regurgitation: quantification using moving slice velocity mapping

Comprehensive assessment of the severity of valvular insufficiency includes quantification of regurgitant volumes. Previous methods lack reliable slice positioning with respect to the valve and are prone to velocity offsets due to through-plane motion of the valvular plane of the heart. Recently, the moving slice velocity mapping technique was proposed. In this study, the technique was applied for quantification of mitral and aortic regurgitation. Time-efficient navigator-based respiratory artifact suppression was achieved by implementing a prospective k-space reordering scheme in conjunction with slice position correction. Twelve patients with aortic insufficiency and three patients with mitral insufficiency were studied. Aortic regurgitant volumes were calculated from diastolic velocities mapped with a moving slice 5 mm distal to the aortic valve annulus. Mitral regurgitant flow was indirectly assessed by measuring mitral inflow at the level of the mitral annulus and net aortic outflow. Regurgitant fractions, derived from velocity data corrected for through-plane motion, were compared to data without correction for through-plane motion. In patients with mild and moderate aortic regurgitation, regurgitant fractions differed by 60% and 15%, on average, when comparing corrected and uncorrected data, respectively. Differences in severe aortic regurgitation were less (7%). Due to the large orifice area of the mitral valve, differences were still substantial in moderate-to-severe mitral regurgitation (19%). The moving slice velocity mapping technique was successfully applied in patients with aortic and mitral regurgitation. The importance of correction for valvular through-plane motion is demonstrated.

Assessment of myocardial perfusion in coronary artery disease by magnetic resonance: a comparison with positron emission tomography and coronary angiography

BACKGROUND

Monitoring contrast medium wash-in kinetics in hyperemic myocardium by magnetic resonance (MR) allows for the detection of stenosed coronary arteries. In this prospective study, the quality of a multislice MR approach with respect to the detection and sizing of compromised myocardium was determined and compared with positron emission tomography (PET) and quantitative coronary angiography.

METHODS AND RESULTS

A total of 48 patients and healthy subjects were studied by MR using a multislice hybrid echo-planar pulse sequence for monitoring the myocardial first pass kinetics of gadolinium-diethylenetriamine pentaacetic acid bismethylamide (Omniscan; 0.1 mmol/kg injected at 3 mL/s IV) during hyperemia (dipyridamole 0.56 mg/kg). Signal intensity upslope as a measure of myocardial perfusion was calculated in 32 sectors per heart from pixelwise parametric maps in the subendocardial layer and for full wall thickness. Before coronary angiography, coronary flow reserve (hyperemia induced by dipyridamole 0.56 mg/kg) was determined in corresponding sectors by (13)N-ammonia PET. Receiver-operator characteristic analysis of subendocardial upslope data revealed a sensitivity and specificity of 91% and 94%, respectively, for the detection of coronary artery disease as defined by PET (mean coronary flow reserve minus 2SD of controls) and a sensitivity and specificity of 87% and 85%, respectively, in comparison with quantitative coronary angiography (diameter stenosis >/=50%). The number of pathological sectors per patient on PET and MR studies correlated linearly (slope, 0.94; r=0.76; P<0.0001).

CONCLUSIONS

The presented MR approach reliably identifies patients with coronary artery stenoses and provides information on the amount of compromised myocardium, even when perfusion abnormalities are confined to the subendocardial layer. This modality may qualify for its clinical application in the management of coronary artery disease.

Magnetic resonance-based assessment of global coronary flow and flow reserve and its relation to left ventricular functional parameters: a comparison with positron emission tomography

BACKGROUND

Measurement of coronary sinus blood flow (CSF) by phase-contrast magnetic resonance (PC-MR) imaging at rest and during hyperemia may allow noninvasive assessment of global coronary hemodynamics.

METHODS AND RESULTS

Sixteen healthy volunteers (age, 22 to 32 years) were examined with MR and PET in random order within 1 to 2 days. At rest and during hyperemia (dipyridamole 0.56 mg/kg), CSF was measured by a cine PC-MR technique (temporal resolution, 40 ms; spatial resolution, 1.25x0.8 mm(2)), and myocardial blood flow (MBF) was measured by [(13)N]NH(3) PET. PET and MR agreed closely for coronary flow reserve (CFR; mean difference, 2.2+/-14.7%; Bland-Altman method). CSF divided by either total left ventricular mass or an estimate of drained myocardium (LVM(drain)) correlated highly with PET flow data (r=0.93 and 0.95, respectively) and with measures of oxygen demand, ie, heart rate, afterload-corrected fiber shortening, and peak systolic stress determined by MR (overall correlation coefficients, 0.81 and 0.87, respectively, multivariate analysis). CSF/LVM(drain) did not differ significantly from PET-derived MBF (difference, 3.6+/-16.6%). In orthotopic heart transplant recipients (n=9), CFR was reduced and blood supply-demand relationships at rest were shifted toward higher flows (P<0.0001).

CONCLUSIONS

This integrated MR approach allows comprehensive assessment of autoregulated and hyperemic coronary flow and is suitable for serial measurements in patients. In transplanted hearts, elevated resting flow is the major cause of reduced CFR.

Valvular heart disease: assessment of valve morphology and quantification using MR

For clinical evaluation and decision-making in patients with valvular heart disease, the diagnostic armamentarium expands steadily. This evolution makes it difficult to choose the most appropriate approach for a specific valvular lesion. It may also reflect our uncertainty of what are the findings that best predict clinical outcome of patients, e.g. after surgery. Accordingly, for each type of valvular lesion, some pathopysiological considerations are stated in order to derive the most important measures that would allow optimal guidance of patients. Based on these considerations the value of an MR study is discussed for each valvular lesion. Newest advances in MR technology allow for highly accurate measurements of regurgitant volumes and hence, MR may be the method of choice for a quantitative evaluation of regurgitant valves. For assessment of stenosis severity, measurement of transvalvular pressure gradient is an appropriate measure and MR may not confer benefits over echocardiography, provided the ultrasound window is adequate (and stroke volume is in the normal range). With respect to surgical treatment, valvular morphology is of pivotal importance, particularly for the mitral valve, and echocardiography still appears to be the first line method. Little data relate lesion severity and/or morphology to clinical outcome. Conversely, the extent of cardiac adaptation to pressure- and/or volume-overload, i.e. ventricular remodeling, is a strong predictor of outcome, and is therefore most important for final judgement of the patient. For assessment of left and right ventricular remodeling, echocardiography typically provides all the necessary information. However, in special cases with discrepant findings, with inadequate ultrasound window, or in the preoperative work-up, MR may provide important information regarding cardiac adaptation to valvular lesion.

Influence of felodipine on left ventricular hypertrophy and systolic function in orthotopic heart transplant recipients: possible interaction with cyclosporine medication

BACKGROUND

Concentric left ventricular (LV) hypertrophy develops early in orthotopic heart transplant (OHT) recipients. To compare the effects of a calcium channel blocker, felodipine, versus diuretics on LV hypertrophy and LV systolic function repeated magnetic resonance imaging studies were performed in OHT recipients. Cyclosporine levels and neurohormones were also measured to explore potential interactions with treatment.

METHODS

Twenty-two patients were randomized at baseline (2 months after OHT) to receive felodipine or diuretic treatment. Before and after 4 months of treatment (n = 19), LV dimensions and LV mass (Simpson's rule) were measured. The relationship between circumferential fiber shortening (two-shell cylindrical model) and end-systolic wall stress was used as a measure of load-independent LV contractility. Neurohormones were measured at the beginning and end of the treatment period, and cyclosporine levels and blood pressures were additionally measured during treatment.

RESULTS

At baseline, the felodipine and diuretic groups did not differ in LV mass, wall stress, and fiber shortening. During felodipine treatment LV mass decreased (p < 0.01) and tended to increase during diuretics treatment (p = 0.06). Afterload-corrected fiber shortening did not change during felodipine treatment, but decreased (p < 0.01) with diuretics. Changes in LV mass were positively correlated with cyclosporine levels (r = 0.70) in the diuretics group, but not in the felodipine group.

CONCLUSIONS

In OHT recipients during diuretic treatment, progression of LV hypertrophy occurs in relation to cyclosporine plasma levels and is accompanied by impairment of systolic contractile function. Felodipine induces regression of LV hypertrophy, while systolic contractile function is preserved. During felodipine treatment, regression of LV hypertrophy is unrelated to cyclosporine levels. Thus, felodipine seems to attenuate the hypertrophic effect of cyclosporine on transplanted hearts.

Assessment of myocardial function and perfusion in a canine model of non-occlusive coronary artery stenosis using fast magnetic resonance imaging

Magnetic resonance (MR) functional and perfusion imaging were employed in a canine model of coronary artery stenosis (n = 6) for the quantification of functional and perfusion deficits before and after dipyridamole administration. Left anterior descending and circumflex (LCX) coronary blood flow were measured continuously after placing Doppler flowmeters. Inversion recovery gradient echo images during the transit of MR contrast medium gadolinium-benzyloxypropionictetraacetate dimeglumine (Gd-BOPTA/Dimeg) and fast breath-hold cine MR images were acquired at baseline, during LCX stenosis in basal state, and during LCX stenosis with vasodilation (dipyridamole 0.5 mg/kg). The extent of the functional defect and perfusion defect was expressed as percent of left ventricle (LV) circumference. During stenosis (LCX flow: 62.6 +/- 5.6% of baseline) the extent of the functional defect was slightly larger than the perfusion defect (11.0 +/- 1.8% versus 6.3 +/- 1.70% of LV circumference, respectively; P < 0.01). During vasodilation the extent of the functional defect was considerably smaller than the perfusion defect (25.3 +/- 2.5% versus 35.3 +/- 3.5%; P < 0.01). Thus, the sizes of ischemic regions displayed by MR perfusion defect and functional defect differ from each other.

Influence of severity of myocardial injury on distribution of macromolecules: extravascular versus intravascular gadolinium-based magnetic resonance contrast agents

OBJECTIVES

This study sought to 1) compare the distribution of extravascular (573 Da) and intravascular (92 kDa) magnetic resonance (MR) contrast agents in reperfused infarcted myocardium, and 2) investigate the effect of injury severity on these distribution patterns.

BACKGROUND

Myocardial distribution of low and high molecular weight contrast agents depends on vascular permeability, diffusive/convective transport within the interstitium and accessibility of the intracellular compartment (cellular integrity).

METHODS

To vary the severity of myocardial injury, 72 rats were subjected to 20, 30, 45 or 75 min (n = 18, respectively) of coronary artery occlusion. After 2 h of reflow, the animals received either 0.05 mmol/kg of gadolinium-diethylenetriaminepentaacetic acid-bismethylamide (Gd-DTPA-BMA) (n = 24), (Gd-DTPA)30-albumin (n = 24) or saline (control group, n = 24). Three minutes after injection, the hearts were excised and imaged (spin-echo imaging parameters: repetition time 300 ms, echo time 8 ms, 2-tesla system), followed by triphenyltetrazolium chloride staining for infarct detection and sizing.

RESULTS

Histomorphometric and MR infarct size (expressed as percent of slice surface) correlated well: r = 0.96 for Gd-DTPA-BMA; r = 0.95 for (Gd-DTPA)30-albumin. On Gd-DTPA-BMA-enhanced images, reperfused myocardial infarctions were homogeneously enhanced. The ratio of signal intensity of infarcted/ normal myocardium increased with increasing duration of ischemia (overall p < 0.0001, analysis of variance [ANOVA]), indicating an increase in the distribution volume of Gd-DTPA-BMA in postischemic myocardium. On (Gd-DTPA)30-albumin-enhanced images, reperfused infarctions consisted of a bright border zone and a less enhanced central core. The extent of the core increased with increasing duration of ischemia (overall p value < 0.0001, ANOVA).

CONCLUSIONS

At 2 h of reperfusion, the distribution of MR contrast agents in postischemic myocardium is 1) specific for extravascular and intravascular agents, and 2) modulated by the duration of ischemia.

Quantification of coronary artery volume flow rate using fast velocity-encoded cine MR imaging

OBJECTIVE

Breath-hold velocity-encoded cine (VENC) MR imaging has been proposed as a method for measuring coronary blood flow. However, most studies have measured velocity rather than volume flow rate in the coronary arteries. The purpose of this study was to measure volume flow rate in the coronary artery of dogs using high-speed gradients and to compare MR flow measurements with those obtained with a sonographic flowmeter.

MATERIALS AND METHODS

Fast VENC MR images were obtained with a high-speed-gradient 1.5-T MR system in seven anesthetized dogs before and after administration of dipyridamole. Images were acquired on double oblique planes perpendicular to the left anterior descending arteries with a slice thickness of 5 mm, a field of view of 20 x 10 cm, a velocity window of +/- 1 m/sec, an average imaging time of 21 sec, a TR/TE of 11/5, and a temporal resolution of 44 msec.

RESULTS

Coronary flow measured with VENC MR imaging correlated well with flow measured by the flowmeter (r = .95, slope = 0.97, n = 88). Interobserver variability in measuring coronary flow volume was 8%.

CONCLUSION

Fast VENC MR imaging with high-speed gradients can provide accurate quantification of volume flow rate in coronary arteries.

Assessment of early left ventricular remodeling in orthotopic heart transplant recipients with cine magnetic resonance imaging: potential mechanisms

We performed short axis cine magnetic resonance imaging studies in 11 patients 2 months after they underwent orthotopic heart transplantation (OHT), and in 10 control subjects, to measure left ventricular (LV) volumes, mass, and end-systolic wall stress to assess ventricular remodeling after OHT. Although there were no significant differences in ventricular volumes and ejection fractions between heart transplant recipients and control subjects, heart transplant recipients had significantly higher LV mass (198 +/- 61 vs 132 +/- 27 gm, p = 0.001). As a consequence of myocardial hypertrophy, end-systolic wall stress was significantly reduced in heart transplant recipients compared with control subjects (34 +/- 16 vs 57 +/- 10 kdyne/cm2, p = 0.001). Moreover, heart transplant recipients had significantly reduced end-systolic wall stress/volume ratio when compared with control subjects (0.89 +/- 0.3 vs 1.26 +/- 0.3 kdyne/cm2/ml, p < 0.01), indicating an already reduced LV contractility 2 months after heart transplantation. Univariate regression analysis revealed a significant correlation between LV mass and averaged cyclosporine levels, but no correlation between LV mass and blood pressure, cold ischemic time, acute rejection, age, body mass, blood pressure, plasma catecholamine levels, or plasma renin activity. Magnetic resonance imaging demonstrates early LV remodeling after OHT with reduced myocardial contractility. Cyclosporine may be contributing to these changes.

Normal myocardial perfusion assessed with multishot echo-planar imaging

A new magnetic resonance imaging strategy is presented for accessing myocardial perfusion. Most previous work has relied on using T1-weighted fast gradient-echo imaging to monitor dynamically the signal changes during the passage of a contrast media bolus. However, the gradient-echo approach is limited by an inability to image the entire heart with adequate temporal resolution. This paper focuses on a electrocardiogram-gated multishot echo-planar imaging sequence, using the simple strategy of using the intrinsic T1 weighting produced by a repetition time equal to the heart period. To quantitate the sequence's performance with respect to normal myocardial perfusion, seven volunteers were imaged, each with three different doses of the contrast medium gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). The first-pass dynamics of the contrast were quantified in 13 regions per heart for each examination. In all volunteers, the complete heart could be covered, with five to seven slices, every two heartbeats. Enhancement was homogeneous throughout the left ventricular myocardium, with an enhancement of approximately 50% for the optimum contrast dose of 0.05 mmol/kg Gd-DTPA.

Very fast cardiac imaging

With very fast MR imaging techniques, myocardial perfusion can be assessed by monitoring the changes of myocardial signal intensity over time following bolus injection of a contrast medium. Very fast MR imaging techniques also allow for freezing of cardiac motion that is important for coronary MR angiography and their high temporal resolution allow for coronary flow reserve measurements. In the current overview, basic principles and strategies of very fast cardiac MR imaging are presented. In the second part, applications of these fast sequences in the fields of myocardial perfusion, coronary MR angiography, and low measurements are presented.

Phase-contrast echo-planar MR imaging: real-time quantification of flow and velocity patterns in the thoracic vessels induced by Valsalva's maneuver

Although the clinical manifestations of Valsalva's maneuver are well known, the associated hemodynamic changes in the great vessels have not been extensively studied and documented. In each of six healthy subjects, we evaluated three "quasi-steady-state" phases of Valsalva's maneuver: (1) during normal respiration, (2) during late strain, and (3) 4 seconds after strain release. Continuous flow, velocity, and cross-sectional area measurements were obtained in the superior vena cava, pulmonary trunk, and thoracic aorta with single-shot echo-planar MR imaging (EPI) with velocity-encoded gradients, which provided 256 images in 5 seconds, yielding 26 velocity-encoded images per second. In the superior vena cava, Valsalva's maneuver induced an 11% decrease in average flow volume, a 102% increase in peak flow velocity, a 156% increase in the time velocity integral, and a 37% decrease in cross-sectional area. MR velocity measurements agreed with echocardiographic data and supplied additional information on flow and morphology. EPI showed a reduction in venous return during Valsalva's maneuver by simultaneously assessing flow, velocity, and vessel morphology; this technique appears to be useful in the analysis of flow dynamics of the great vessels.

The internal mammary artery malperfusion syndrome: incidence, treatment and angiographic verification

Internal mammary artery (IMA) malperfusion syndrome is caused by an acute imbalance between myocardial demand and nutritional support through the mammary artery. In a consecutive series of 2326 isolated myocardial revascularizations-with at least one IMA to the left anterior descending branch (LAD) in 91.3% (2125/2326)-we identified 45 patients (1.9%) with a perioperative course suggesting IMA malperfusion syndrome. Additional saphenous vein graft to the distal segment of the LAD was performed during normothermic ventricular fibrillation in all patients. Hospital mortality was 4.4% (2/45), intra-aortic balloon pumping was required in 15.5% (7/45) and anterior myocardial infarction occurred in 28.8% (13/45). Coronary angiography was performed in all survivors between 3 and 24 months postoperatively. Wide patent IMA graft and patent saphenous vein graft were observed in 56% (24/43), narrowed but patent IMA graft and patent vein graft in 35% (15/43), while patent vein graft and not visualized IMA in 7% (3/43); in one patient with severely diseased peripheral LAD, no flow could be demonstrated in the IMA graft or in the additional vein graft (1/43, 2.4%). No major differences were found between early and late coronary angiography in these patients. Additional vein graft to distal LAD is the treatment of choice in acute IMA malperfusion syndrome. Despite patent vein graft with superior blood flow, early and late postoperative IMA flow to LAD is maintained in the majority of patients.

Small infarctions of cochlear, retinal, and encephalic tissue in young women

BACKGROUND AND PURPOSE

Recently, a rare syndrome that involves uniformly the brain, inner ear, and retina in previously healthy young women has been described. Brain biopsies and ophthalmologic examinations disclosed small infarcts as a pathoanatomical substrate of the disease. In previous reports, an autoimmune disorder or a coagulopathy have been suggested as possible etiologies.

CASE DESCRIPTIONS

Both patients (aged 22 and 20 years) had brain involvement with neurological and neuropsychological deficits. Multifocal small hyperintensities were shown in magnetic resonance imaging of the brain. Findings of cerebrospinal fluid examination and electroencephalography were pathological in case 1 and of cerebral angiography in case 2. Both patients had a neurosensory hearing loss and multiple retinal branch arteriolar occlusions. Both women were on fenfluramine before onset of the disease. In case 1, attacks recurred during a follow-up of 34 months. At onset of the disease the 5-hydroxyindoleacetic acid and homovanillic acid levels of the cerebrospinal fluid were reduced; 13 months later the 5-hydroxyindoleacetic acid level was still reduced and the homovanillic acid level was low-normal. In case 2, with the longest follow-up of 13 years, the disease was active during only the initial 2 1/4 years. During this period a combination of oral anticoagulant and antiplatelet agents was ineffective.

CONCLUSIONS

Our findings could not support current etiologic hypotheses. Whether changes in 5-hydroxyindoleacetic acid and homovanillic acid levels in the cerebrospinal fluid and/or fenfluramine intake play a role in the pathogenesis of the disease remains to be elucidated.

Myocardial oxygen consumption in aortic valve disease with and without left ventricular dysfunction

OBJECTIVE

To assess whether and to what extent myocardial oxygen consumption is modified by hypertrophy and alterations in contractility in patients with aortic valve disease and to evaluate the influence of regression of left ventricular hypertrophy and improvement of contractility on myocardial oxygen consumption after successful aortic valve replacement.

DESIGN

A cohort analytical study to investigate the influence of the "explanatory" variables of myocardial oxygen consumption by multiple regression analysis. A comparison of myocardial oxygen consumption in preoperative patients with that after operation in a group with comparable severity of aortic valve disease before operation (analysis of covariance).

PATIENTS

In six controls and in 43 patients with aortic valve disease and normal coronary arteries standard haemodynamic variables were measured, left ventricular biplane cineangiography performed, and coronary sinus blood flow measured by thermodilution. The patients were divided into three groups: 19 preoperative patients with normal ejection fraction (greater than or equal to 57%) (group 1); nine preoperative patients with reduced ejection fraction (less than 57%) (group 2); 16 postoperative patients (one with preoperative and postoperative measurements (group 3). Postoperative evaluation was performed 12-51 months after surgery.

MAIN OUTCOME MEASUREMENTS

Myocardial oxygen consumption/100 g left ventricular muscle mass and its suspected "explanatory" variables--that is, peak systolic left ventricular circumferential wall stress, heart rate, contractility (assessed by left ventricular ejection fraction), and left ventricular muscle mass index.

RESULTS

Multiple regression analysis showed that the product of peak systolic stress and heart rate (p less than 0.0001) and ejection fraction (p less than 0.03) were positively correlated with myocardial oxygen consumption/100 g and that left ventricular muscle mass index (p less than 0.002) was negatively correlated with myocardial oxygen consumption/100 g (r = 0.72; n = 50 measurements). Myocardial oxygen consumption per 100 g at a given stress-rate product was higher in the controls than in group 1 (hypertrophied ventricles with normal ejection fraction) and was also higher in group 1 than in group 2 (hypertrophied ventricles with reduced ejection fraction). In a subgroup of the postoperative patients with complete regression of hypertrophy and normalisation of contractility, myocardial oxygen consumption per 100 g at a given stress-rate product was indistinguishable from that in controls.

CONCLUSIONS

When the actual stress-rate product was used as an index of overall left ventricular performance the results suggested that mechanical efficiency was increased in hypertrophied ventricles especially when contractility was decreased. These changes in mechanical efficiency seemed to be reversible during the postoperative course when muscle mass and contractility returned to normal.

[Brain abscess as a complication of Osler's disease with lung involvement]

Eight months after sustaining a reversible left motor hemisyndrome, predominantly of the arm, a 47-year-old man known to have hereditary haemorrhagic telangiectasia (Osler's disease) again developed neurological symptoms (headache, vertigo, unsteady gait) with fever (up to 38.5 degrees C). Clinical features and findings on computed tomography indicated a cerebellar abscess. This was resected because it continued to enlarge despite antibiotic treatment with daily 2 g ceftriaxone and twice daily 0.5 g ornidazole. As another manifestation of Osler's disease further tests revealed an arteriovenous malformation (2.5 x 2.0 cm) in the right upper lobe of the lung, presumably the cause of the cerebral abscess. After wedge resection of the anterior upper lobe segment the further course was without complications.

[Actinomycosis--clinical and therapeutic considerations based on 2 personal case reports]

We report on two patients with actinomycosis. The first case was a 45-year-old cachectic man with extensive bilateral pulmonary infiltrates. The lesions remained unclear for 18 months and only open lung biopsy with microscopic and cultural evaluation led to the diagnosis of actinomycosis. In the second case, classic cervico-facial actinomycosis in a 69-year-old farmer is described. Diagnosis was established on the basis of microscopic findings of "sulphur granules" eroding the mandible. Furthermore, the clinical presentation, with an indurated swelling of the jaw and intraoral fistula formation, was typical. The patient had a severe combined aortic valve lesion and died after ventricular fibrillation during hospitalization. Diagnosis could not be confirmed by culture, probably due to antibiotic prophylaxis against endocarditis during tooth extraction on the first day of admission. Diagnostic difficulties and microbiologic aspects are discussed, with special focus on the rare species of Actinomyces meyeri which was cultured from biopsy specimens from the lung of the first patient. So far this species has been described in only 13 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary reserve in patients with aortic valve disease before and after successful aortic valve replacement

In patients with aortic valve disease and normal coronary angiograms coronary reserve was determined by the coronary sinus thermodilution technique. Three groups of patients were studied: 37 preoperative patients; 18 different patients 12-52 months after aortic valve replacement and seven control subjects with no cardiac disease. Coronary flow ratio (dipyridamole/rest) was diminished in preoperative compared with postoperative patients (1.66 +/- 0.44 vs 2.22 +/- 0.85; P less than 0.05) as well as with controls (2.80 +/- 0.84; P less than 0.01), and corresponding coronary resistance ratio (dipyridamole/rest) was higher in preoperative patients than in both other groups (0.61 +/- 0.17 vs 0.48 +/- 0.14; P less than 0.05 vs 0.37 +/- 0.10; P less than 0.01). Differences in the flow ratio, but not in the resistance ratio, were significant (P less than 0.05) in patients after aortic valve replacement compared with controls. Total coronary sinus blood flow at rest was elevated in preoperative compared with both postoperative patients and controls (252 +/- 99 vs 169 +/- 63; P less than 0.01; vs 170 +/- 35 ml.min-1, P less than 0.05), whereas flows after maximal vasodilation did not differ among the three groups (416 +/- 184 vs 361 +/- 150 vs 488 +/- 235 ml.min-1). Postoperative patients showed a distinct, though not total regression of left ventricular angiographic muscle mass index and wall thickness. Nine of the 18 postoperative patients showed a normal coronary flow reserve and nine showed subnormal response. These two subgroups did not differ with respect to preoperative macroscopic and microscopic measures of hypertrophy. Thus in aortic valve disease, the reduced coronary vasodilator capacity is mainly due to an elevated coronary flow at rest, while the maximal coronary blood flow achieved is identical to that of postoperative patients and controls. With regression of left ventricular hypertrophy, flow at rest decreases and this leads to a distinct improvement of coronary flow reserve.