Reshaping the Ventricle From Within

Visual Abstract

snare prepositioned within the predilatated posterobasal ventricular wall ( Figure 1E, Video 1), and the anchor guidewire is withdrawn. The resulting venovenous guidewire rail ( Figure 1F) is exchanged for ultra-high molecular weight polyethylene braided Cardiac function was assessed using CMR at 0.55-T (Prototype MAGNETOM Aera, Siemens). 14 The interpapillary distance was the center of mass between the papillary endocardial surfaces at end-systole on short-axis CMR.   sequence is shown in Figure 1.  In cardiomyopathic ventricles, there was a biphasic response in myocardial performance to progressive MIRTH circumferential shortening ( Figures 6D to 6G).
With initial shortening, load-independent measures of contractility (Ees and PRSW) and ventricular mechanical efficiency increased. Other parameters also changed with progressive MIRTH shortening. PVA changed inversely with Ees; PVA changes are proportional to myocardial oxygen demand. 17,18 V o changed concordantly with Ees. After a peak, additional shortening degraded performance (Table 3).
Importantly, optimum shortening coincided with an inflection in the shortening LVEDP curve ( Figure 6H).
By contrast, in healthy ventricles, only Ees increased with MIRTH shortening, to a threshold above which additional shortening reduced Ees ( Figures 6A to 6C).
As expected, other measures of myocardial performance did not improve with MIRTH shortening in healthy ventricles ( Table 3). In cardiomyopathic ventricles, the optimum range of MIRTH circumferential shortening that improved indexes of myocardial performance was 17% to 21%.  Values are median (quartile 1-quartile 3). a Excluding separated implants. b P < 0.01, c P < 0.05, and d P < 0.001 compared with baseline value using the Wilcoxon signed rank test.

MIRTH AT BASE VERSUS MIDMYOCARDIAL LEVEL.
We tested whether circumferential MIRTH induced different remodeling responses when applied at the midventricular level compared with the basal level ( Figure 2). Basal and mid MIRTH implants reduced left ventricular chamber volumes comparably on CMR ( Table 2). The net global function by all measures of strain (longitudinal, radial, and circumferential) was also similar (P ¼ NS). By contrast, regional strain analysis revealed remote increases in the base and apex for midventricular implants and in the mid and apical ventricle for basal implants (Figure 2).  Figure 3C).

DISCUSSION
We describe MIRTH, a fully percutaneous, transvenous, regional, circumferential, left ventricular  In MIRTH, we steer a commercially available angioplasty guidewire freely within the walls of the left ventricle. After the addition of a 30 to 40 CTO tip bend, and once delivered to the ventricular myocardium, a combination of forward and rotational movements grants the ability to "navigate" with multiple degrees of freedom. We show that wires can be steered at will to accomplish any desired intramyocardial position (eg, from base to apex, apex to base, endocardium to epicardium, epicardium to endocardium, and obliquely in either direction and at any depth) irrespective of myofiber orientation. 20 We modified this guidewire technique from transcatheter mitral cerclage 11,21 wherein we traverse the interventricular septum with a guidewire from a septal perforator vein into the right ventricular infundibular cavity. In our U.S. feasibility study, 22 we observed that a CTO angulated tip afforded great versatility in septal guidewire navigation. Such guidewire manipulation does not recognizably injure the myocardium or induce epicardial bleeding.
Identifying the guidewire tip position has proven difficult using conventional imaging modalities, which suffer from poor soft tissue definition, off-axis imaging planes, and poor intramyocardial device     Abbreviation as in Tables 1 and 2. extensive radiofrequency ablation or chemoablation (eg, at the basal interventricular septum ["summit"] or the base of the papillary muscles 32 ).