Ann Thorac Surg 2000;70:1115-1118
© 2000 The Society of Thoracic Surgeons
Supplement: cardiothoracic techniques & technologies
Instrumental validation of percutaneous transmyocardial revascularization: follow-up data at one year
Alessandro S. Bortone, MD, PhDa,b,c,
Donato D’Agostino, MDa,b,c,
Stefano Schena, MDa,b,c,
Giuseppe Rubini, MDa,b,c,
Maurizio Viecca, MDa,b,c,
Vito Sardaro, MDa,b,c,
Antonella Tucci, MDa,b,c,
Luigi de Luca Tupputi Schinosa, MDa,b,c
a Department of Emergency and Transplantation, Division of Cardiac Surgery, University of Bari School of Medicine, Bari, Italy
b Institute of Nuclear Medicine, University of Bari School of Medicine, Bari, Italy
c Division of Cardiology, "L. Sacco" Hospital, Milan, Italy
Address reprint requests to Dr Bortone, Haemodynamic Laboratory, Division of Cardiac Surgery, University of Bari, Ospedale Consorziale Policlinico, Pizza G. Cesare, 11, 70124 Bari, Italy
e-mail: emobort{at}libero.it
Presented at the Sixth Annual Cardiothoracic Techniques and Technologies Meeting 2000, Ft Lauderdale, FL, Jan 27–29, 2000.
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Abstract
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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.
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Introduction
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Up to date, despite the progresses of coronary artery operation and interventional radiology techniques, there is a significant number of patients with severe ischemic heart disease who are refractory to medical management and not suitable for conventional therapy such as percutaneous transluminal coronary angioplasty or coronary artery bypass grafting because of severe distal vessel disease or totally occluded coronary arteries [1, 2]. Therefore, transmyocardial laser revascularization (TMR) has been developed as a new treatment that results in a significant reduction in severity of angina and improvement of exercise capability, quality of life, and myocardial perfusion [2].
Possible mechanisms to explain the clinical benefits of TMR include the stimulation of angiogenesis, local myocardial denervation, or both [3]. However, the surgical approach of TMR is affected by 10% to 19% perioperative mortality and a relevant morbidity [2].
A nonsurgical, percutaneous, catheter-based TMR laser system (PTMR) has been developed [4]. Light energy from a holmium-YAG (yittrium-aluminum-garnet) laser (Holmium-YAG; Eclipse Surgical Technologies, Sunnyvale, CA) is emitted by an optical fiber contained in a catheter introduced through the common femoral artery. The laser beam is directed to the left ventricular cavity into the myocardium, allowing a controlled creation of nontransmural laser channels, smaller in size but comparable in effects on tissues to the surgical TMR procedure [4, 5].
The development of the current PTMR technique was propelled by the belief that holmium-YAG laser energy could be used to ablate myocardial tissue through an endocardial approach, thereby achieving effects closer to those obtained by TMR through the epicardial approach [4, 5].
The aim of the present study was to validate the proved clinical efficacy of PTMR, by instrumental evaluations as single photon emission tomography (SPET) and transthoracic echocardiography (TTE) analysis of myocardial treated areas.
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Material and methods
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Patients were divided in two groups as follows: Group A comprised 27 patients (19 men and 8 women, 63 ± 10 years) complaining of angina pectoris, who underwent 99mTc-sestamibi SPET rest versus stress test before and after PTMR treatment, to obtain information about myocardial perfusion; group B comprised 30 patients (21 men and 9 women, 65 ± 8 years) with similar symptoms, who underwent transthoracic 2D-Echo Doppler (TTE) with automatic border detection before and after PTMR to identify left ventricular volumes remodelling and the end-systolic subendocardial layer thickness and, thereafter, to evaluate the cardiac function.
To exactly measure the left ventricular wall thickness, all 57 patients underwent a 2D-Echo Doppler immediately before PTMR. Only myocardial segments with an end-diastolic wall thickness up to 9 mm were treated and standard hemodynamic parameters were evaluated during the procedure.
Percutaneous transmyocardial revascularization was performed safely and without any complications for each patient as described previously. Briefly, after local anesthesia with xylocaine 2%, a 9F deflectable guiding catheter was inserted percutaneously in the common right femoral artery and advanced in a 0.035-inch Teflon-covered guidewire (260 cm length) that was introduced in the left ventricle through a standard 6F pig-tail catheter, also used for the two control left ventriculographies performed before and after the treatment. Thereafter, a 4F optical fiber with 2.5 J constant tip energy emissions, was advanced inside the guiding catheter to reach the treated areas. The Eclipse laser emitted a burst of five pulse waves for each application; the first and the second are usually performed for autocalibration and the last three to advance through the myocardium, to obtain channels of 1 mm in diameter and from 2 to 5 mm in depth.
Patients in group A underwent 99mTc-sestamibi SPET (740 + 740 MBq) rest versus stress test before PTMR (base line values) and at 4, 12, 24, and 48 weeks from treatment, to identify reversible defects of the ischemic areas. The SPET (Fig 1) was performed using a 
counter (GE 4000 XT, Waukesha, WI) with a low-energy and high-resolution collimator (64 x 64 matrix, 64 views, 25 sec/view).
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Fig 1. (A) 99mTc-Sestamibi at rest (CCS angina class IV); the white arrow indicates perfusion defects in a myocardial segment. (B) 99mTc-Sestamibi rest versus stress, in the same patient, 12 months following PTMR. A white arrow shows the absence of perfusion defects in the treated segment both at rest and at the peak of the stress test.
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Patients in group B underwent TTE (HP Sonos 5500, Hewlett Packard, Palo Alto, CA) evaluation before PTMR (base line values) and at 1, 4, 12, and 24 weeks from treatment, to estimate ventricular volumes, Doppler flow, and the end-systolic subendocardial layer thickness (Fig 2). A software for automatic border detection and volumes evaluation was used.
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Fig 2. Transthoracic echocardiography evaluation with automatic border detection and left ventricular Doppler flow, before and after PTMR, showing the improvement of (A) myocardial contractility at the peak of systolic flow (white arrow) and (B) the end-systolic subendocardial layer thickness before and 7 days after the treatment.
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All patients underwent an ergometric stress-test (according to Bruce’s protocol) before PTMR and during each time point of the follow-up.
Statistical analysis was performed by one-way analysis of variance for repeated measures. The global level of statistical significance was set at 5%.
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Results
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The clinical data of group A and B patients as well as the number and site of laser channels are reported in Table 1. Follow-up data of all 57 treated patients are reported in Table 2. There was a highly significant reduction of CCS angina class immediately after the PTMR procedure (p < 0.0001) that persisted throughout the whole follow-up. A slight, but significantly improved duration of exercise tolerance was observed only during the follow-up (p < 0.05), whereas no significant variations were found in heart rate, total time to significant ST depression, and maximal stress-test double product (HR x systolic BP, see Table 2).
An increased perfusion without reversible defects at rest and at the peak of stress test was found in 75% of treated patients in group A. The improved myocardial perfusion persisted in the follow-up at 12 months (Fig 1).
Patients in group B exhibited a global, but not significant reduction of all ventricular volumes associated with no significant variations in ejection fraction and a slight but not significant improvement of left ventricular systolic Doppler flow signal.
On the other hand, an improvement in the end-systolic subendocardial layer thickness was observed in 73% of the group B patients, both in the period immediately following PTMR and during the follow-up (Fig 2).
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Comment
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Despite the proved clinical efficacy of PTMR in patients affected with critical coronary artery disease, the pathophysiologic mechanisms responsible for the beneficial effect of this technique are still unclear [4, 5]. Moreover, myocardial perfusion evaluations with 201 Tl-scintigraphy show controversial results. Some studies have reported improved perfusion in myocardial regions treated with TMR whereas other studies argued these data [6, 7]. One explanation could be that 201 Tl-scintigraphy is not sensitive enough to show improved perfusion in small areas of the left ventricle.
The more sensible 99mTc-sestamibi SPET was used in the present study with the aim to evaluate the myocardial perfusion in treated regions. We found that an improvement of myocardial perfusion was present in 75% of the treated patients both at rest and at the peak of the stress test, and persisted during the follow-up at 12 months.
An improved perfusion of subendocardial regions with positron emission tomography study following TMR was reported [8]. Nevertheless, an improved perfusion by using the same positron emission tomography technique was not found by some authors [7].
For this reason, TTE was adopted in the present study, to evaluate the remodeling of the subendocardial layer. Our data clearly demonstrated the increase of the end-systolic subendocardial layer thickness in 73% of the treated patients, which persisted in the follow-up at 6 months.
Despite the reported improvement in CCS angina class, which did not vary during the follow-up, and the total stress-test duration (Table 2), a slight, but not significant, reduction of all ventricular volumes without variation of global ejection fraction was found in our patients. The reason for nonsignificant improvement of the global cardiac function could be that both the improvement of myocardial perfusion and consequently of the end-systolic subendocardial layer thickness are sufficient to provide relief from angina but not enough to improve the global ventricular function.
In conclusion, PTMR is a new, safe, and feasible technique that allows surgeons to treat patients with severe ischemic heart disease who have no indications for either coronary artery bypass grafting or percutaneous transluminal coronary angioplasty. The controversies about the ability of this technique to increase myocardial perfusion are strictly related to the sensitivity of scintigraphic techniques used for myocardial evaluation. Indeed, the detection of the improved subendocardial layer perfusion was performed with sophisticated techniques (SPET, TTE) to correctly estimate the results derived from PTMR treatment.
These preliminary data indicate the possibility of clinical benefit because of the improvement of symptoms, myocardial perfusion, and systolic performance of the left ventricle. However, it is necessary to continue with randomized studies to compare the effect of PTMR with conventional medical treatments in patients with severe ischemic heart disease.
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Acknowledgments
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We thank Michele Sciascia, MS, and the CathLab personnel for significant contribution. We also thank Mrs Katia Surdo for secretarial assistance.
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References
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Abstract
Introduction
