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MRI of Cardiac Morphology and Function After Percutaneous Transluminal Septal Myocardial Ablation for Hypertrophic Obstructive Cardiomyopathy

¹ Department of Radiology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8603, Japan.
² First Department of Internal Medicine, Nippon Medical School, Tokyo 113-8603, Japan.

Received February 25, 2003; accepted after revision August 19, 2003.

 
Address correspondence to Y. Amano.

Abstract

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OBJECTIVE. The objective of our study was to use MRI to show the cardiac morphology and function of patients with hypertrophic obstructive cardiomyopathy after percutaneous transluminal septal myocardial ablation.

CONCLUSION. Black blood T2-weighted and contrast-enhanced fast inversion recovery gradient-echo images displayed ablated septal myocardium until 35 weeks after percutaneous transluminal septal myocardial ablation. Central hypointense areas were observed on MRI in patients until 4 weeks after ablation. Black blood and cine steady-state free precession MRI were used to assess the decreased septal wall thickness and diameter of the left atrium after ablation as well as the reduced motion of the ablated region. MRI may be useful for evaluation of cardiac structural, signal, and functional changes associated with percutaneous transluminal septal myocardial ablation.

Introduction

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Hypertrophic obstructive cardiomyopathy is characterized by asymmetric septal myocardial hypertrophy that results in obstruction of the left ventricular outflow tract and an increased pressure gradient between the left ventricle and ascending aorta [1]. This outflow tract gradient can lead to diastolic dysfunction, chronic heart failure, and sudden death. Percutaneous transluminal septal myocardial ablation has recently been used as a nonsurgical procedure to treat hypertrophic obstructive cardiomyopathy [2–4]. The left ventricular outflow tract gradient can be directly monitored during ablation. If this pressure gradient increases during the follow-up period, the procedure can be repeated.

Conventional catheter angiography reveals the septal branches of the left anterior descending artery and allows the left ventricular outflow tract gradient to be directly monitored before and after ablation [2–4]. However, this technique is too invasive to be used for follow-up monitoring of the gradient and the left ventricular ejection fraction. Echocardiography can be used to measure the pressure gradient and ejection fraction of the left ventricle non-invasively and to visualize the motion of the myocardial wall [3]. The disadvantages of echocardiography include low reproducibility, a limited acoustic window, and an inability to identify ablated myocardium.

MRI is used to investigate various cardiac disorders, including hypertrophic obstructive cardiomyopathy, because it has high spatial and contrast resolution, a wide range of view, high reproducibility, and a variety of attendant techniques [5–8]. On MRI, heart morphology and myocardial damage can be identified, and estimates can be made of the left ventricular ejection fraction, the left ventricular outflow tract gradient, and the coronary flow reserve [6–10]. Cine steady-state free precession imaging provides excellent contrast between the myocardium and the chambers, greatly improving the visualization of myocardial wall motion [8]. However, only a few reports have been made on MR assessment of both structural and functional cardiac changes in patients with hypertrophic obstructive cardiomyopathy after percutaneous transluminal septal myocardial ablation [7, 11].

The aim of our study was to use MRI to evaluate the effects of percutaneous transluminal septal myocardial ablation on hypertrophic obstructive cardiomyopathy. To our knowledge, ours is the first report describing the structural and functional cardiac changes associated with this procedure in both the ablated and nonablated regions.

Subjects and Methods

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Patients
From October 2000 to May 2003, 15 patients with hypertrophic obstructive cardiomyopathy were recruited to participate in our study. Patients gave informed consent, and the study protocols were approved by our institutional review board. The indications for percutaneous transluminal septal myocardial ablation were based on data from previous reports [2–4]: resistance to negative inotropic drugs, associated chronic heart failure, a left ventricular outflow tract gradient of more than 40 mm Hg, or septal hypertrophy thicker than 15 mm. Six men and nine women (age range, 15–80 years; mean, 52.1 years) constituted our sample population. Eleven of the 15 patients underwent one procedure—one septal branch was ablated in nine patients and two septal branches were ablated in two patients. The remaining four patients were treated twice—two or three septal branches were ablated in each patient. The dose of injected absolute ethanol ranged from 0.8–3.3 mL per vessel (mean ± SD, 1.88 ± 0.65 mL) and from 2.0–6.4 mL per patient (3.11 ± 1.52 mL). Eleven MR examinations were performed before percutaneous transluminal septal myocardial ablation in 11 patients, and 19 examinations were performed after ablation in 15 patients. Eleven of the 15 patients underwent one MR examination, and the remaining four patients received two examinations after ablation. Three examinations were performed 2–4 weeks after the latest ablation, 11 were performed 5–13 weeks after ablation, three were performed 24–35 weeks after ablation, and two were performed 12 months or more (12 and 18 months) after ablation.

MRI Protocol
MR examinations were performed using a 1.5-T MR imager (Signa CV/i, General Electric Medical Systems, Milwaukee, WI). A cardiac phased array coil was used for signal reception. Breath-hold transverse black blood T2-weighted fast spin-echo imaging with cardiac gating and a double inversion recovery pulse pair were performed with or without fat suppression [11]. Typical imaging parameters were: TR, 2 cardiac cycles; TE, 85 msec; echo-train length, 32; receiver bandwidth, 100 kHz; imaging matrix, 160–320 x 224–256; field of view, 36–40 x 36–40 cm; and section thickness, 8 mm with a gap of 2 mm. The time between the double inversion recovery pulse pair and data acquisition was determined automatically to suppress the flow signal in the selected section [10]. Breath-hold cardiac-gated segmented cine steady-state free precession or fast spoiled gradient-echo (SPGR) imaging was performed in the long- and short-axis planes. Steady-state free precession imaging (TR range/TE range, 3.9–4.7/1.6–2.0; view per segment, 16–24; flip angle, 45–60°; receiver bandwidth, 125 kHz; imaging matrix, 256 x 128–160; field of view, 32 x 32 cm; and section thickness, 8 mm, with 2-mm gap) was mainly used because it provides good contrast between the myocardium and the ventricular chamber [8]. We used view-sharing to double the cardiac phases to 16–24. The last nine MR examinations in eight patients were contrast-enhanced inversion recovery fast gradient-echo imaging sequences (5.5/1.4; flip angle, 20°; inversion time, 250 msec) performed in the short-axis plane 10 min after a 0.15-mmol/L injection of gadolinium. The in- and through-plane spatial resolutions were identical to those of cine images.

Imaging Analysis
In nine MR examinations, we used black blood T2-weighted fast spin-echo imaging to investigate the signal intensity of the septal myocardial wall before percutaneous transluminal septal myocardial ablation. In 19 examinations, we used this sequence to investigate the signal change associated with the ablation with regard to the interval between the ablation and the MR study. In addition, we performed nine examinations to study the delayed hyperenhancement of the septal myocardium associated with ablation. Next, we estimated septal and posterior wall thicknesses at end diastole, the ratio between septal wall and posterior wall thicknesses, the anteroposterior diameter of the left atrium at diastole, and the left ventricular ejection fraction in 11 patients. The border between the myocardium and the left ventricular chamber was traced manually on the MRIs and the papillary muscles were excluded from the endocardial border when the ejection fraction was estimated using Simpson's rule.

Thirteen MRIs obtained after the first ablation provided cine MRIs of sufficient image quality to allow us to quantitatively evaluate the septal wall motion using the percentage of systolic wall thickening present. We determined the percentage of systolic wall thickening with the following formula: (end-systolic septal wall thickness – end-diastolic septal wall thickness) / end-diastolic septal wall thickness x 100. We then compared the percentage of systolic wall thickening of the ablated and nonablated regions of the septal wall. The ablated region was defined as the area of the myocardium fed by the ablated septal arteries and showing abnormal hyperintensity on black blood T2-weighted fast spin-echo images, delayed hyperenhancement, or focal atrophy. The nonablated region was defined as the apical septal wall that showed neither abnormal signals nor atrophy.

To compare the quantitative parameters before and after percutaneous transluminal septal myocardial ablation or between the ablated and nonablated regions, we used a paired Student's t test. The differences were considered statistically significant at a p value exceeding 0.05.

Results

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The signal change and delayed hyperenhancement after percutaneous transluminal septal myocardial ablation with regard to the interval between the ablation and the MR examination are summarized in Figure 1. We found that the myocardium in patients with hypertrophic obstructive cardiomyopathy presented homogeneously low signal intensity on black blood T2-weighted fast spin-echo images (Fig. 2A). On T2-weighted fast spin-echo and contrast-enhanced inversion recovery fast gradient-echo images obtained within 35 weeks of ablation, the ablated myocardium showed focal high signal intensity and delayed hyperenhancement (Figs. 2B and 2C). The septal myocardium and adjacent myocardium were isointense on the two MRIs obtained 12 and 18 months after ablation (Fig. 3A, 3B). Two patients, who underwent MRI 11 and 13 weeks after ablation, showed no high signal intensity on black blood T2-weighted fast spin-echo images but did exhibit delayed hyperenhancement on contrast-enhanced MRIs. A central hypointense area was observed in the ablated regions in two of the three patients who underwent MRI within 4 weeks of the ablation (Figs. 2B and 2C).

View larger version (18K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1. —Bar graph shows MRI detection rates of high signal intensity and delayed hyperenhancement in ablated septal wall after percutaneous transluminal septal myocardial ablation in patients with hypertrophic obstructive cardiomyopathy. Black bar represents detection rate for black blood T2-weighted fast spin-echo imaging, and white bar represents detection rate for contrast-enhanced inversion recovery fast gradient-echo imaging. Values at top of bars indicate number of patients whose images showed focal hyperintensity or delayed hyperenhancement of total number of patients who were examined with each technique. Both black blood T2-weighted fast spin-echo and contrast-enhanced inversion recovery fast gradient-echo imaging depicted ablated region clearly. A = Two of three patients who underwent MRI within 4 weeks of ablation showed central hypointense regions in ablated septal wall. B = In two patients, no focal high signals were identified in septal wall, but delayed hyperenhancement was visualized on contrast-enhanced MRI.

View larger version (121K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2A. —56-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Black blood T2-weighted fast spin-echo image obtained before ablation shows hypertrophic septal wall.

View larger version (123K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2B. —56-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Fat-suppressed black blood T2-weighted fast spin-echo (B) and contrast-enhanced inversion recovery fast gradient-echo images (C) obtained 4 weeks after ablation show focal high signal intensity and delayed hyperenhancement in septal wall and central hypointense region is observed in ablated region (arrow, B and C).

View larger version (119K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2C. —56-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Fat-suppressed black blood T2-weighted fast spin-echo (B) and contrast-enhanced inversion recovery fast gradient-echo images (C) obtained 4 weeks after ablation show focal high signal intensity and delayed hyperenhancement in septal wall and central hypointense region is observed in ablated region (arrow, B and C).

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3A. —80-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Comparison of fat-suppressed black blood T2-weighted fast spin-echo image obtained before ablation (A) with that obtained 12 months after ablation (B) shows that septal wall thickness has decreased, but no signal changes are observed (arrows, B).

View larger version (132K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 3B. —80-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Comparison of fat-suppressed black blood T2-weighted fast spin-echo image obtained before ablation (A) with that obtained 12 months after ablation (B) shows that septal wall thickness has decreased, but no signal changes are observed (arrows, B).

The septal and posterior wall thicknesses, the ratio between the septal wall and posterior wall thicknesses, the diameter of the left atrium, and the left ventricular ejection fraction before and after percutaneous transluminal septal myocardial ablation are summarized in Table 1. We found significant decreases in septal wall thickness (p < 0.0012) and in the left atrium diameter at end diastole (p < 0.012) after ablation but found no significant changes in the posterior wall thickness, the ratio between the septal wall and posterior wall thicknesses, or the ejection fraction (p > 0.10).

In all patients, the percentage of systolic wall thickening after ablation was lower in the ablated region of the septal wall (Figs. 2D and 2E) than in the nonablated region (Figs. 2F and 2G) (16.0 ± 8.0 mm in the ablated region vs 45.0 ± 18.0 mm in the nonablated region, p < 0.01).

View larger version (126K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2D. —56-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Comparison of cine steady-state free precession images obtained at end diastole (D) and end systole (E) in ablated region with those obtained at end diastole (F) and end systole (G) in nonablated region showing reduction of septal wall motion in ablated region (arrows, E).

View larger version (117K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2E. —56-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Comparison of cine steady-state free precession images obtained at end diastole (D) and end systole (E) in ablated region with those obtained at end diastole (F) and end systole (G) in nonablated region showing reduction of septal wall motion in ablated region (arrows, E).

View larger version (133K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2F. —56-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Comparison of cine steady-state free precession images obtained at end diastole (D) and end systole (E) in ablated region with those obtained at end diastole (F) and end systole (G) in nonablated region showing reduction of septal wall motion in ablated region (arrows, E).

View larger version (116K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 2G. —56-year-old woman with hypertrophic obstructive cardiomyopathy who underwent percutaneous transluminal septal myocardial ablation. Comparison of cine steady-state free precession images obtained at end diastole (D) and end systole (E) in ablated region with those obtained at end diastole (F) and end systole (G) in nonablated region showing reduction of septal wall motion in ablated region (arrows, E).

Discussion

Top Abstract Introduction Subjects and Methods Results Discussion References

 
The major findings of our study were that MRI performed after percutaneous transluminal septal myocardial ablation revealed the ablated region and showed decreases in septal wall thickness and atrial diameter and that cine MRI showed reduced wall motion in the ablated region.

Black blood T2-weighted fast spin-echo and contrast-enhanced inversion recovery fast gradient-echo images depicted the ablated region of the septal wall as focal high signal intensity and hyperenhancement, which suggests iatrogenic myocardial infarction [9–12]. Central hypointense areas in the ablated region were observed on the T2-weighted fast spin-echo and contrast-enhanced MRIs within 4 weeks of ablation, which suggests microcirculatory obstruction and coagulation [9, 10]. On the other hand, MRI findings obtained more than 12 months after ablation showed no signal changes in the septal wall. These myocardial signal changes were similar to those of myocardial infarction [12]. In the two patients who underwent MRI within approximately 3 months of ablation, no signal changes were detected in the septal wall on black blood T2-weighted fast spin-echo imaging, but delayed hyperenhancement was identified. The reasons for this finding remain unknown, but contrast-enhanced inversion recovery fast gradient-echo imaging can reveal the dilated interstitial space and scarring associated with percutaneous transluminal septal myocardial ablation in addition to myocardial damages and interstitial edema that may be identified on T2-weighted MRI [9, 10, 12].

MRI showed decreases in septal wall thickness and left atrial diameter after percutaneous transluminal septal myocardial ablation. The decrease in septal wall thickness resulted from the direct effects of the ablation on the septal myocardium [8]. The decrease in left atrial diameter may have been caused by the reductions of mitral regurgitation and end-diastolic left ventricular pressure induced by the ablation. These reductions can contribute, to some extent, to the improvement of diastolic dysfunction [1]. However, we found no significant changes in posterior wall thickness or the ejection fraction. These results suggest that percutaneous transluminal septal myocardial ablation is an efficient procedure for rapidly decreasing septal wall thickness and end-diastolic pressure in the left ventricle [3, 4], but no effects on global heart morphology and function are induced. This finding may be explained by the fact that the myocardial infarction induced by ablation was limited to the septal wall, whereas myocardial disarray and fibrosis may diffusely underlie the myocardium in hypertrophic obstructive cardiomyopathy even before treatment [1, 2]. Cine MRI showed that the wall motion in the ablated region was significantly reduced compared with the motion in the nonablated region. Thus, during a single examination, cardiac MRI techniques provided high contrast resolution to show regional changes in both cardiac morphology and function associated with ablation.

This preliminary study had several limitations that should be addressed. First, the sample size was relatively small, and MRI examinations were performed serially in only four patients. Additionally, a comparative study of contrast-enhanced MRIs and T2-weighted MRIs obtained in a large population should be performed. We did not measure the left ventricular outflow tract gradient. In our study population, we needed a velocity-encoding value greater than 6 m/sec (based on the gradient value estimated by echocardiography), which was not possible to achieve with our MRI unit. Lastly, the myocardial tagging was not included in our imaging protocol partly because the tag diminished before end systole in the patients with bradycardia. However, a refined tagging technique may help delineate the degree and extent of the changes in septal wall motion after percutaneous transluminal septal myocardial ablation.

In conclusion, black blood T-2 weighted, contrast-enhanced inversion recovery fast gradient-echo, and cine steady-state free precession MRI were useful for evaluating the signal changes in, reduced thickness of, and decreased motion in the septal wall after percutaneous transluminal septal myocardial ablation. These regional myocardial changes and the decrease in left atrial diameter were revealed on cardiac MRI.

References

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1. Maron BJ, Bonow RO, Cannon RO, et al. Hypertrophic cardiomyopathy: interrelations of clinical manifestations, pathophysiology, and therapy. N Engl J Med1987; 316:780 –789[Medline]
2. Sigwart U. Non-surgical myocardial reduction for hypertrophic obstructive cardiomyopathy. Lancet1995; 346:211 –214[Medline]
3. Seggewiss H, Gleichmann U, Faber L, Fassbender D, Schmidt HK, Strick S. Percutaneous transluminal septal myocardial ablation in hypertrophic obstructive cardiomyopathy: acute results and 3-month follow-up in 25 patients. J Am Coll Cardiol1998; 31:252 –258[Abstract/Free Full Text]
4. Gietzen FH, Leuner CJ, Raute-Kreinsen U, et al. Acute and long-term results after transcoronary ablation of septal hypertrophy (TASH): catheter interventional treatment for hypertrophic obstructive cardiomyopathy. Eur Heart J1999; 20:1342 –1354[Abstract/Free Full Text]
5. Semelka RC, Tomei E, Wagner S, et al. Interstudy reproducibility of dimensional and functional measurements between cine magnetic resonance studies in the morphologically abnormal left ventricle. Am Heart J 1990;119:1367 –1373[Medline]
6. Jarvinen VM, Kupari MM, Poutanen VP, Hekali PE. Right and left atrial phasic volumetric function in mildly symptomatic dilated and hypertrophic cardiomyopathy: cine MR imaging assessment. Radiology1996; 198:487 –495[Abstract/Free Full Text]
7. Schultz-Menger J, Strohm O, Waigand J, Uhlich F, Dietz R, Friedrich MG. The value of magnetic resonance imaging of the left ventricular outflow tract in patients with hypertrophic obstructive cardiomyopathy after septal artery embolization. Circulation2000; 101:1764 –1766[Abstract/Free Full Text]
8. Carr JC, Simonetti O, Bundy J, Li D, Pereles S, Finn JP. Cine MR angiography of the heart with segmented true fast imaging with steady-state precession. Radiology2001; 219:828 –834[Abstract/Free Full Text]
9. Wu KC, Zerhouni EA, Judd RM, et al. Prognostic significance of microvascular obstruction by magnetic resonance imaging in patients with acute myocardial infarction. Circulation1998; 97:765 –772[Abstract/Free Full Text]
10. Simonetti OP, Finn JP, White RD, Laub G, Henry DA. "Black-blood" T2-weighted inversion-recovery MR imaging of the heart. Radiology1996; 199:49 –57[Abstract/Free Full Text]
11. Sievers B, Moon JCC, Pennell DJ. Images in cardiovascular medicine: magnetic resonance contrast enhancement of iatrogenic septal myocardial infarction in hypertrophic cardiomyopathy. Circulation2002; 105:1018[Free Full Text]
12. Krauss XH, van der Wall EE, van der Laarse A, et al. Follow-up of regional myocardial T2 relaxation times in patients with myocardial infarction evaluated with magnetic resonance imaging. Eur J Radiol 1990;11:110 –119[Medline]

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