Percutaneous Transmyocardial Revascularization Research Articles

Ultrasound device for axial ranging

A treatment tool such as a catheter, MIS or other surgical tool apparatus for placement within a heart chamber, organ aperture or other body opening and axial ranging therein, the apparatus particularly adapted for laser-assisted percutaneous transmyocardial revascularization (MTR). At the distal end of the tool is an annular ultrasound transducer with associated structure, positioned to transmit ultrasound signals substantially axially aligned with the axis of the treatment tool to the cardiovascular tissue, the transducer further receiving returning signals from the cardiovascular tissue to be treated. In a preferred embodiment, the transducer comprises a piezoelectric crystal material. The transducer assembly is attached to the distal tip of the tool such that a laser delivery means or other functional device can be extended through the lumen of the tool and the annular ultrasound transducer. In a preferred embodiment, the invention is a modular ultrasound device capable of being detachably attached to a steerable catheter, MIS or other surgical tool apparatus. The system also comprises a signal interface extending from the ultrasound transducer and signal processing component operatively connected to the signal interface for real time determination of at least one boundary surface of cardiovascular tissue relative to one or more positions of the distal tip of the treatment tool. A method of delivering laser energy to tissue is disclosed, the method including the steps of positioning the firing tip of a laser delivery means adjacent the front surface of the tissue, delivering laser energy to the tissue, transmitting ultrasound energy to the tissue, receiving ultrasound signals reflected from at least the rear surface of the tissue, and determining the distance betwveen the firing tip of the laser delivery means and the rear surface of the tissue. In a preferred embodiment, the method includes quantitative determination of the contractility or motion of the beating heart, such that changes in the depth of tissue can be used to control the channel depth or other treatment parameters. Retrolasing can also be achieved by mechanically piercing the tissue to a determined depth based on axial ranging measurements, and retracting the treatment tool while simultaneously delivering laser energy therefrom.

Outcomes following percutaneous coronary intervention in patients previously considered "without option": a subgroup analysis of the PACIFIC Trial.

The present study assesses clinical outcomes in patients from the Potential Angina Class Improvement From Intramyocardial Channels (PACIFIC) trial of percutaneous transmyocardial revascularization (PTMR) who had previously been considered "no-option," but who subsequently underwent percutaneous coronary intervention (PCI) for continuing symptoms. Patients with advanced symptomatic coronary artery disease who are not candidates for coronary artery bypass grafting (CABG) or PCI comprise an important group, for which no established treatment is currently available. These patients have been described as having "no option," and are currently targeted for various experimental therapies. One such proposed therapy, PTMR, was recently examined in the PACIFIC trial. A subgroup of patients in this trial subsequently underwent PCI, although to initially qualify for the study they had previously been considered as unsuitable for PCI and as having "no option." The therapeutic benefit of PCI for patients of this type is unknown. A retrospective analysis was performed on data obtained from all subjects of the PACIFIC study who underwent PCI within the 12-month follow-up period. Ten subjects originally randomized to PTMR and 11 subjects from the medical treatment group underwent PCI. Most had undergone at least one prior PCI and at least one CABG, and there was a high prevalence of cardiovascular risk factors. Despite excellent immediate procedural success, PCI resulted in only modest, statistically nonsignificant increases in mean exercise duration, small improvements in angina status, and no significant improvements in quality of life. These data suggest that PCI provides only marginal-if any-symptomatic benefit in these patients.

Direct myocardial revascularization and therapeutic angiogenesis.

Interest in direct myocardial perfusion began when Pratt, in 1898, observed persistent myocardial contraction for several hours in ex vivo feline ventricles directly perfuse through the semilunar valves. In 1933 Wearn described ‘myocardial sinusoids’ bathing reptilian ventricular myocytes that do not contain any significant blood supply from the coronary vasculature, eluting the possibility of direct myocardial perfusion via channels from the ventricles. Sen later tested this theory by mechanically creating channels, through direct needle puncture (acupuncture) in the myocardium; short-term reduction in the magnitude of myocardial infarcts and decreased mortality in the treatment group were observed. However, many newly created channels closed with scar tissue over time. Interest in direct myocardial revascularization was revived in the 1970s when lasers were shown to create channels with minimal damage to surrounding tissues. Direct myocardial revascularization, either surgical or catheter-based, is the creation of communicating channels between the left ventricular cavity and ischaemic myocardial tissues via transmyocardial revascularization and percutaneous transmyocardial revascularization modalities. In transmyocardial revascularization (Fig. 1), channels are created directly from the epicardium to the endocardium of the chronically ischaemic, yet viable (hibernating) left ventricular myocardium using lasers or via mechanical means (needle puncture) during open chest surgery. Although the method used in channel creation is similar in percutaneous transmyocardial revascularization (Fig. 2), channels are produced from the endocardium to the ischaemic myocardium using

A prospective, multicenter, randomized trial of percutaneous transmyocardial laser revascularization in patients with nonrecanalizable chronic total occlusions

ObjectivesWe sought to evaluate the safety and efficacy of percutaneous transmyocardial revascularization (PTMR) in patients with refractory angina caused by one or more chronic total occlusions (CTOs) of a native coronary artery. BackgroundPrevious unblinded, randomized trials of PTMR in patients with end-stage coronary artery disease and refractory angina have demonstrated significant relief of angina and increased exercise duration. Whether such benefits would be realized in blinded patients with less extensive coronary artery disease is unknown. MethodsA total of 141 consecutive patients with class III or IV angina caused by one or more chronically occluded native coronary arteries in which a percutaneous coronary intervention (PCI) had failed were prospectively randomized, at 17 medical centers, in the same procedure, to PTMR plus maximal medical therapy (MMT) (n = 71) or MMT only (n = 70). Blinding was achieved through heavy sedation, dark goggles and the concurrent performance of PCI in all patients. ResultsBaseline characteristics were similar between the two groups. A median number of 20 laser channels were created in patients randomized to PTMR. At six months, the anginal class improved by two or more classes in 49% of patients assigned to PTMR and in 37% of those assigned to MMT (p = 0.33). The median increase in exercise duration from baseline to six months was 64 s with PTMR versus 52 s with MMT (p = 0.73). There were no differences in the six-month rates of death (8.6% vs. 8.8%), myocardial infarction (4.3% vs. 2.9%) or any revascularization (4.3% vs. 5.9%) in the PTMR and MMT groups, respectively (p = NS for all). ConclusionsIn patients with class III or IV angina caused by nonrecanalizable CTOs, the performance of PTMR does not result in a greater reduction in angina, improvement in exercise duration or survival free of adverse cardiac events, as compared with MMT only.

Intramyocardial delivery of FGF2 in combination with radio frequency transmyocardial revascularization.

Therapeutic angiogenesis and percutaneous transmyocardial revascularization (PMR) are potentially synergistic modalities to improve myocardial perfusion. To evaluate the efficiency of FGF2 delivery into an area that has been radio frequency (RF) ablated, we studied two catheter-based delivery methods, a direct injection system (Stiletto) and a combined RF ablation-delivery system (RF-PMR). Four groups (n = 3/group) of pigs received six transendocardial injections of (125)I-FGF2/fluorescent microspheres with either the Stiletto or the RF-PMR catheter. RF-PMR injections were preceded by a 0.6 sec RF ablation step. After either 1 or 24 hr, hearts and other tissues were harvested. Intramyocardial deposition sites were located with UV light and isolated. Specific activity per site was expressed as a percentage of total activity injected per site corrected for quenching. Injection site recovery was high for both catheter systems (average = 88%) and systemic uptake was low (< 6% in the liver). FGF2 retention was significantly higher with the Stiletto than the RF-PMR catheter (Stiletto 1 hr 41% +/- 17%, 24 hr 26% +/- 10%, RF-PMR 1 hr 21% +/- 14%, 24 hr 13% +/- 8%; P < 0.001), principally explained by the differences in catheter design. The Stiletto has a retractable needle and is optimized for intramyocardial delivery, whereas infusion from the RF-PMR device occurs at the endocardial surface and relies on channels created during RF ablation. Overall, FGF2 retention after transendocardial intramyocardial delivery by the Stiletto or the RF-PMR system is significantly higher than previously observed for intracoronary, intravenous and intrapericardial delivery. In conclusion, the combination of RF ablation and growth factor delivery using the RF-PMR system is feasible and efficient. Cathet Cardiovasc Intervent 2001;53:429-434.

Instrumental validation of percutaneous transmyocardial revascularization: follow-up data at one year

Background. Despite the clinical efficacy of percutaneous transmyocardial revascularization (PTMR), up to date there are still no instrumental validations to demonstrate both the improved perfusion of treated areas and cardiac function. Methods. During the first year of follow-up after PTMR, 27 patients (group A) underwent 99mTc MIBI exercise-single photon emission tomography (SPET), while 30 patients (group B) underwent serial transthoracic echocardiography (TTE) evaluations with analysis of cardiac volumes and subendocardial layer thickness in systole. Results. All 57 patients had a significant angina Canadian Cardiovascular Society (CCS) class improvement. Group A patients (75%) had improved exercise-SPET perfusion in treated areas at 12 weeks after PTMR, and at the next follow-up. Group B patients had non-significant reduction in global volume and no significant change in ejection fraction. However, there was an improvement in thickness of the subendocardial-treated areas in systole that persisted during follow-up. Conclusions. The use of SPET and TTE validates the clinical efficacy of PTMR.

Results from late-breaking clinical trials sessions at ACCIS 2000 and ACC 2000

### One-year follow-up of patients with refractory angina randomized to percutaneous transmyocardial revascularization versus medical therapy Emerson C. Perin, MD, FACC Texas Heart Institute, Houston, Texas Percutaneous transmyocardial revascularization (PTMR) has previously been reported to be

Percutaneous transmyocardial laser revascularization: overview of US clinical trials.

Data from four surgical trials of laser transmyocardial revascularization (TMR) show pain reductions of at least two classes occurred among 25-76% of patients, significantly greater than with optimal medical therapy. The safety and feasibility of percutaneous TMR (PTMR) was proved in multiple uncontrolled registry studies. With PTMR in two randomized trials enrolling about 550 patients, improvements were found among 45% and 66% of patients as compared with 13% for best medical therapy. Other encouraging observations included significant improvements in exercise time (85 and 100 seconds) as compared with minimal or negative results for medical therapy, consistent overall exercise time improvements for PTMR, and overall patient perceptions of anginal stability and global health. Peri-procedural mortality is low and ranged from 0% to 0.6%. Some skepticism remains about the procedures, arising from failure in most cases to show improvements with SPECT imaging and lack of conclusive insights into the mechanism of action. A randomized 'blinded' study is underway to establish a definitive therapeutic value for catheter-based TMR. Nonetheless, preliminary clinical data seem promising for catheter-based TMR for obtaining symptomatic improvement in patients with chronic refractory ischemic coronary syndromes.

PTMR. Percutaneous transmyocardial revascularization.

When all options are exhausted, percutaneous transmyocardial revascularization can diminish symptoms of angina.

Percutaneous transmyocardial revascularization induces angiogenesis: a histologic and 3-dimensional micro computed tomography study.

The purpose of this study was to visualize the spatial patterns and connection of channels created after percutaneous transmyocardial revascularization (PTMR) in normal porcine hearts, and to estimate the relative contributions of transmyocardial and coronary perfusion. Six pigs underwent PTMR creating channels using radiofrequency ablative energy. Three-dimensional computed tomography imaging of channels 1 hr after PTMR showed the direct connection of PTMR channels to the myocardial capillary network and to epicardial coronary vessels. In the heart, examined 28 day after PTMR, there was a fine, extensive, network of microvessels originating from the site of the original PTMR channel, also connecting the left ventricular cavity to myocardial capillaries. Histopathologic examination of the 1-hr specimens showed numerous regions of myocardial hemorrhage and associated inflammatory cell infiltration. In the 28-day specimens, newly developed new vascular network suggested neovascularization within the core of these channel remnants. The immunoreactivity for basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) were intense within myocardium and neovascular structure surrounding PTMR channel remnants. The vascular connections occur by direct communication with existing myocardial vasculature acutely, and angiogenesis in these channel remnant chronically.

Medical Applications of Fiber-Based Optical Power Delivery.

This paper reviews the current status of fiber-based optical power delivery for medicine and its applications to minimally invasive therapeutics and diagnostics. Quartz glass fibers, hollow fibers, and infrared glass/crystalline fibers are used for the power transmission of medical lasers. The characteristics of these fibers and fiber-based medical laser devices are described. For clinical applications, fibers are used in combinationwith catheters, endoscopes, or cannulas. Catheter-based applications include laser angioplasty, laser thrombolysis, and PTMR (Percutaneous Trans-Myocardial Revascularization). The endoscope allows the delivery of optical power not only for coagulation but also for tissue removal (ablation). Endoscopes for PDT (PhotoDynamic Therapy) are also developed. For cannula-based applications, PLDD (Percutaneous Laser Disk Decompression), ILCP (Interstitial Laser Coagulation of Prostate), and TUBAL-T (TransUrethral Balloon Thermotherapy) are described. For use in fiber-based optical biopsies, the principle and apparatus of a fluorescence imagingsystem for early cancer detection and an OCT (Optical Coherence Tomography) are introduced.