Patients with end-stage heart failure (HF) may require advanced therapeutics to recover their failing heart. However, current clinical profiles and biomarkers do not adequately predict which therapeutic is appropriate. Myocardial perfusion reserve and fibrosis, which can be measured with MRI, may be important predictors for guiding advanced therapeutics. However, patients with end-stage HF often have implantable cardioverter defibrillators (ICD), which induces severe image artifacts that render standard perfusion MRI useless. We had developed a novel cardiac T1 mapping method [1] using BISTRO [2] as a wideband saturation pulse for measuring diffuse myocardial fibrosis in patients with ICD. In this study, we implemented BISTRO as a wideband saturation pulse to enable first-pass myocardial perfusion MRI in patients with end-stage HF.

Pulse Sequence: We implemented optimized BISTRO as a train of 4 adiabatic hyperbolic secant pulses (each pulse duration = 2.82 ms, net frequency bandwidth = 9.2 kHz) into a cardiac perfusion MRI pulse sequence using TurboFLASH readout. For convenience, we call this method wideband perfusion MRI. We then compared the performance between wideband and standard cardiac perfusion MRI in 4 human subjects (see below for more details). Conventional perfusion MRI sequence utilized a train of three 90˚ rectangular pulses as the saturation pulse (net frequency bandwidth = 2.9 kHz). Both pulse sequences used identical image parameters, including: FOV = 360 mm x 270 mm (PE), slice thickness = 8 mm, acquisition matrix = 192 x 144 (PE), TE = 1.3 ms, TR = 2.7 ms, readout duration = 194 ms, receiver bandwidth = 1000 Hz/pixel, flip angle = 12˚, acceleration factor (GRAPPA) = 2, linear k-space ordering, inversion time = 106 ms.

Subject: We recruited four healthy volunteers (two males; age = 32.7 ± 6.7 yrs). To mimic a realistic situation, we taped an ICD (VITALITY AVT, Boston Scientific) on the left breast, approximately 5-10 cm away from heart [1,3]. All subjects provided written informed consent.

MR Imaging: We imaged 4 subjects on a 3T MRI system (Prisma, Siemens). (Residual Mz after saturation pulse) Prior to Gd-BOPTA administration, we performed saturation-no-recovery experiment to calculate residual longitudinal magnetization (Mz) after wideband and standard saturation pulses, as previously described [4]. This experiment was conducted in a 2-chamber plane, as the image artifact is often seen in the anterior wall. (First-pass Perfusion MRI) Each subject underwent two perfusion MRIs with 30 min delay between the first and second perfusion MRI acquisitions, where each perfusion MRI was conducted with 0.075 mmol/kg of Gd-BOPTA. The pulse sequence order was randomized to minimize potential bias.

Image Analysis: We calculated residual Mz by dividing the T1-weighted image by the proton density image (i.e., equilibrium magnetization). We calculated mean residual Mz for seven myocardial segments in a 2-chamber view [5]. For perfusion MRI, to compare signal intensities between different segments, we normalized the T1-weighted images by a proton density weighted image. This process corrects for surface coil inhomogeneity.

Figure 1 shows severe image artifacts using a standard perfusion MRI sequence. Note that the same artifacts disappear with a wideband perfusion MRI pulse sequence. Averaging the results over 4 subjects (Figure 2), for each segment, the mean residual Mz values were higher for standard than wideband pulse sequences. Figure 3 shows perfusion images pre-contrast, at peak blood enhancement, and at peak wall enhancement. Note that artifacts are visible in standard images, whereas they are suppressed in wideband images. Normalized signal-time curves of artifact-affected and remote zones illustrate this difference (see Figure 4). Figure 5 shows standard and wideband perfusion images at peak blood enhancement for subjects 2-4. In all four cases, standard perfusion MRI produced image artifacts, whereas wideband perfusion MRI suppressed image artifacts. This study demonstrated feasibility of wideband cardiac perfusion MRI for assessment of perfusion reserve in patients implanted with ICD. This new perfusion MRI sequence, in conjunction with wideband late gadolinium-enhanced (LGE) MRI [3] and wideband cardiac T1 mapping [1], may enable comprehensive assessment of cardiac health in patients with end-stage HF for guiding advanced therapeutics. .