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Ann Thorac Surg 1998;66:998-1001
© 1998 The Society of Thoracic Surgeons

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Supplement

The LAST operation: techniques and results before and after the stabilization era

^a Division of Cardiac Surgery, "G. D’Annunzio" University, Chieti, Italy

Address reprint requests to Dr Calafiore, Division of Cardiac Surgery, "G. D’Annunzio" University, S Camillo de’Lellis Hospital, via C. Forlanini, 50 66100 Chieti, Italy
e-mail: (calafiore{at}unich.it)

Presented at "Facts and Myths of Minimally Invasive Cardiac Surgery: Current Trends in Thoracic Surgery IV," New Orleans, LA, Jan 24, 1998.

Abstract

Background. Left anterior descending artery stabilization allows performance of left internal mammary artery grafting via a left anterior small thoracotomy on a beating heart. Our surgical experience was reviewed to assess if surgical results have improved as result of specialized instrumentation.

Methods. Of 545 patients who had the left anterior small thoracotomy operation, 261 underwent this procedure for single left anterior descending artery disease. Two groups were considered, before and after the use of specialized instrumentation: group A (n = 93), operated on from November 21, 1994, to April 20, 1996; and group B (n = 168), operated on from April 21, 1996, to December 1997.

Results. Early mortality was similar in the two groups. The further revascularization (operation or percutaneous transluminal coronary angioplasty) and the rate of occlusion of the conduit were higher in group A, whereas anastomotic or conduit malfunction was not. Cumulating angiography and Doppler flow evaluation, 92.5% of the anastomoses in group A and 98.8% in group B (p = 0.026) were patent, and 90.3% in group A and 97.6% in group B (p = 0.031) were patent and not restrictive. At 19 months, survival was similar, but the event-free survival was higher in group B.

Conclusions. Both left anterior descending artery stabilization and safer left internal mammary artery harvesting contributed to improve angiographic and clinical results after the left anterior small thoracotomy operation.

Left anterior descending (LAD) coronary artery grafting using the left internal mammary artery (LIMA) through a left anterior small thoracotomy (LAST) had new popularity staring in 1994, when Benetti and Ballester [1] revisited this approach after the pioneering work of Kolessov [2]. Whereas in the beginning the operation was performed with the same tools normally used in conventional coronary artery grafting, later many companies proposed different instruments to help in LIMA harvesting and in properly stabilizing the LAD.

We herein review our surgical experience related to patients who underwent the LAST operation for single LAD disease before and after the stabilization era.

Material and methods

Patients
From November 21, 1994, to December 20, 1995, 261 patients of 545 LAST operations underwent this procedure for single LAD disease.

Surgical indications were type C lesions (176), cardiologist’s or patient’s preference (56), and restenosis after percutaneous transluminal coronary angioplasty or stenting of the proximal LAD (29). In 9 more patients (3.3%) the operation was indicated, but for different reasons they had to be converted to a median sternotomy.

The patients were divided into two groups, according to the period in which they were operated on, before or after the use of specialized instrumentation in our surgical technique: group A (n = 93), from November 21, 1994, to April 20, 1996 (first period); and group B (n = 168) from April 21, 1996, to December 20, 1997 (second period). Table 1 shows the clinical data of both groups.

In group B, LIMA was harvested with the aid of a special retractor (LIMA Lift; Cardio Thoracic Systems, Cupertino, CA), usually for a longer segment (mean length, 9.5 ± 3.7 cm). Left anterior descending coronary artery stabilization was obtained pharmacologically (diltiazem, intravenously) and mechanically (Platform Access, Cardio Thoracic Systems). The anastomosis was always performed using two sutures. Quality control of the anastomosis was obtained with angiography and with Doppler flow evaluation, at rest and during an Azoulay maneuver [4]. Moreover intraoperative flow measurement in the operating room was added (Cardio-Med CM 2008, Oslo, Norway; Transonic System Inc, Ithaca, NY). Perioperative data are shown in Table 2.

A few hour later, the patients were transferred to the ward. The drain and the intrapleural catheter were removed on the morning of the first postoperative day. A new echo Doppler flow velocity assessment was then repeated, at rest and during the Azoulay maneuver. Acute hypervolemia is induced by first passively lifting both legs of the patient, then releasing the legs to allow the patient to perform an isometric exercise; this is associated with an increase of cardiac output and heart rate. If the echo Doppler flow is recorded at rest and during the Azoulay maneuver, an increase of the diastolic flow can be observed. Angiographic studies clearly demonstrate that this pattern is characteristic of a nonrestrictive anastomosis.

Many patients had a postoperative angiography, mainly for study purposes. However, every patient who was believed to have an anastomotic malfunction had an angiography.

In the morning of the second postoperative day, many patients were discharged. The great majority of the remaining waited only for the control angiography.

Statistical analysis
Results are expressed as mean ± standard deviation unless otherwise indicated. Statistical analysis comparing the two groups was performed with unpaired two-tailed Student’s t test for the means, or ² test for categoric variables. Survival and event-free survival curves were obtained with the Kaplan-Meier method (BMDP 1L software, Los Angeles, CA). The statistical significance was calculated with the Mantel-Cox test and z-test. A p value of less than 0.05 was considered significant.

Results

A direct anastomosis of LIMA to LAD was obtained in 245 patients (93.9%), 83 in group A and 162 in group B (89.2% versus 96.4%; not significant [NS]). A saphenous vein graft (2 cases) or an inferior epigastric artery (14 cases) were used to elongate the LIMA in the remaining (10.8% in group A and 4.6% in group B; NS). Perioperative and postoperative data are shown in Tables 2 and 3.

Conversion rate was similar in both groups, 4 in group A and 5 in group B (4.3% versus 3.0%; NS). Causes of conversion were not visible LAD in 6 patients (3 versus 3), small-sized LAD in 1 (0 versus 1), and calcified LAD in 2 (1 versus 1).

During the first 30 days after the operation, 1 patient in group B died suddenly (0% versus 0.6%; NS) (overall mortality rate 0.4%); necropsy showed patent anastomosis without clear signs of myocardial infarction or ischemia. Only 1 patient died late in group A, owing to a multiorgan failure, 36 days after simultaneously undergoing carotid endoarterectomy, femorofemoral bypass, and LAST operation. Bleeding from an LIMA collateral caused hypotension, and renal failure was the primary cause of the problems. After a follow-up of 50 ± 115 days, 10 patients (3.8%) had a surgical redo because of anastomotic or conduit failure, 7 in group A and 3 in group B (7.5% versus 1.8%; NS). Two patients (0.8%) had a percutaneous transluminal coronary angioplasty, after a mean of 23 ± 5 days, both in group A (2.1% versus 0%, NS). Cumulating surgical redo and percutaneous transluminal coronary angioplasty, the incidence of further revascularization was lower in group B (1.8% versus 9.7%; p < 0.001; mean of 70 ± 140 versus 11 ± 13 days; p < 0.001).

Quality control of the anastomosis
One hundred seventy-seven patients (67.8%) had an early postoperative angiography, 61 in group A and 117 in group B (65.6% versus 69.6%; NS). Nine conduits (5.1%) were occluded, 7 in group A and 2 in group B (11.5% versus 1.7%; p = 0.022). As the LAD was not involved, the cause of closure was considered related to conduit injury and not to anastomotic failure. Four (2.2%) showed a grade B [5] anastomotic or conduit malfunction, 2 in group A and 2 in group B (3.3% versus 1.7%; NS). One patient in group B showed reversal of conduit malfunction, from grade B to grade A, 110 days after the first angiography. Cumulating angiography and Doppler flow evaluation, 96.6% of the anastomoses were patent (92.5% in group A and 98.8% in group B; p = 0.026) and 95.4% were patent and nonrestrictive (90.3% in group A versus 97.6% in group B; p = 0.031).

Clinical results
After a mean follow-up of 16.5 ± 9.9 months (26.5 ± 6.3 in group A and 10.1 ± 5.4 months in group B; p < 0.001), 259 patients (99.2%) are alive and asymptomatic (92 [98.9%] in group A and 167 [99.4%] in group B; NS), 247 are alive, asymptomatic, and without redo or percutaneous transluminal coronary angioplasty (83 [89.2%] in group A and 164 [97.6%] in group B; p = 0.01). No patients had acute myocardial infarction. Thirty-seven–month actuarial survival was 99.6%, and event-free survival was 93.6% in the whole surgical experience. Comparing survival between groups, after 19 months (the longest follow-up in group B), there was no statistical difference (99.0% ± 1.0% in group A versus 99.3% ± 0.7% in group B) (Fig 1). However, 19-month event-free survival was higher in group B than in group A (95.8% ± 1.5% versus 89.9% ± 2.6%; p = 0.05) (Fig 2).

View larger version (9K): [in this window] [in a new window]   Fig 1. Actuarial survival at 19 months in group A (solid line) and group B (dotted line) (ns = not significant.)

View larger version (9K): [in this window] [in a new window]   Fig 2. Event-free survival at 19 months in group A (solid line) and group B (dotted line).

Introduction into the clinical practice of specialized instrumentation allowed a wider spread of performing LIMA to LAD grafting through a LAST. Many concerns were related, in fact, to the possibility of doing a perfect anastomosis on a beating heart. As LIMA patency is by far the most important determinant of survival and event-free survival after coronary revascularization [6], LAD stabilization allowed us to reproduce the conditions of the arrested heart. However, in our opinion, this was not the most important technical aspect that characterized the second period.

Left internal mammary artery harvesting became safer, as the possibility of a better exposure of the conduit allowed us to dissect the graft minimizing the possibility of injuries. As a matter of fact, reduction of conduit occlusion was a crucial technical improvement, as shown by comparison of the two periods (11.5% in group A versus 1.7% in group B; p = 0.022). Moreover the harvested conduit was longer than in the first period, halving the incidence of elongation necessity, although the absolute values were not statistically significant.

Quality control of the anastomosis became more complete. After the anastomosis was accomplished, a flowmeter was used, giving us immediately an initial idea about graft patency. The Doppler flow assessment, at rest in the intensive care unit, confirmed the presence of a diastolic flow. The same evaluation, performed on the first postoperative day during the Azoulay maneuver, gave more information about the function of the anastomosis in a stress condition [4]. Of course angiography, performed in 67.8% of the patients, was the best instrument to validate the anatomy of the conduit and of the anastomosis.

The anastomosis was accomplished using one suture and, later on, two sutures. Mechanical stabilization, even though it made the anastomosis technically easier, did not affect the percentage of anastomotic malfunction (3.3% in group A versus 1.7% in group B; NS).

We think that the cause of improved results in group B is multifactorial. Our learning curve ended at the beginning of that period and our experience in identifying anastomotic malfunction increased. As a consequence the incidence of further revascularization decreased significantly, and we had an improvement in event-free survival. However, the angiographic results obtained during our global experience are comparable with the recently reported data from the IMAGE trial [7], in which 645 patients who, after LIMA to LAD grafting through a median sternotomy with conventional cardiopulmonary bypass, underwent angiography a mean of 10.8 days after surgery. In this group patency rate was 98.8% (94.9% in our global experience and 98.3% in group B) and patency rate with less than 50% anastomotic or conduit stenosis was 90.5% (92.7% in our global experience and 96.6% in group B).

In conclusion, the LAST operation left its infancy and became a safe and reproducible procedure. Specialized instrumentation made the operation easier and contributed to its widespread use together with an end of the learning curve and increased experience.

References

1. Benetti F.J., Ballester C. Use of thoracoscopy and a minimal thoracotomy, in mammary-coronary bypass to left anterior descending artery, without extracorporeal circulation. Experience in 2 cases. J Cardiovasc Surg (Torino) 1995;36:159-161.[Medline]
2. Kolessov V.I. Mammary artery–coronary artery anastomosis as method of treatment for angina pectoris. J Thorac Cardiovasc Surg 1967;54:535-544.[Medline]
3. Calafiore A.M., Di Giammarco G., Teodori G., et al. Left anterior descending coronary artery grafting via left anterior small thoracotomy without cardiopulmonary bypass. Ann Thorac Surg 1996;61:1658-1665.[Abstract/Free Full Text]
4. Calafiore A.M., Teodori G., Di Giammarco G., et al. Minimally invasive coronary artery bypass grafting on a beating heart. Ann Thorac Surg 1997;63:S72-S75.
5. Fitzgibbon G.M., Kafka H.P., Leach A.J., Keon W.J., Hooper G.D., Burton J.R. Coronary bypass graft fate and patient outcome: angiographic follow-up of 5065 grafts related to survival and reoperation in 1388 patients during 25 years. J Am Coll Cardiol 1996;28:616-626.[Abstract]
6. Loop F.D. Internal thoracic artery grafts—biologically better coronary arteries. N Engl J Med 1996;334:263-265.[Free Full Text]
7. Berger P.B., Alderman E.L., Schaff H.V. Frequency of early occlusion and stenosis in the left internal mammary artery among patients undergoing CABG through a median sternotomy on conventional bypass: benchmark for the MIDCAB. Circulation 1997;96(Suppl 1):680.

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