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J Thorac Cardiovasc Surg 1998;115:148-151
© 1998 Mosby, Inc.

SURGERY FOR CONGENITAL HEART DISEASE

The "H" graft: An alternative approach for performing minimally invasive direct coronary artery bypass

From the Division of Cardiothoracic Surgery, Department of Surgery,Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass.

Received for publication June 3, 1997. Accepted for publication August 29, 1997. Revisions requested July 30, 1997; revisions received August 27,1997. Address for reprints: William E. Cohn, MD, Beth Israel DeaconessMedical Center, 330 Brookline Ave., Dana 905, Boston, MA 02215.

	Abstract

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Objectives: Minimallyinvasive direct coronary artery bypass permits arterial revascularizationwithout cardiopulmonary bypass, potentially decreasing associated morbidity.The procedure is, however, technically challenging and associated with significantpostoperative pain resulting from retraction through the small incision.
Methods and patient selection:> From December 1996 to April 1997, eight patients underwent grafting of theleft anterior descending coronary artery by use of a short segment of rightinferior epigastric artery attached proximally to the side of an in situ leftinternal thoracic artery. We have termed this procedure the "H"graft MIDCAB.
Results: No patients required intraoperative conversion to conventional bypass.No postoperative deaths or myocardial infarctions occurred. Six patients withnormal renal function underwent postoperative angiography that demonstratedgraft patency with rapid filling of the left anterior descending coronaryin each case. Postoperatively clinical signs of acute ischemia were resolvedor a normal exercise tolerance test was obtained in all patients. The medianpostoperative length of stay was 3 days. Rib spreading and chest wall retractionwere not required in any procedure.
Conclusions: The "H" graft procedure is anattractive alternative to standard minimally invasive bypass because of greatertechnical simplicity, the avoidance of internal thoracic artery harvest, andexcellent visualization with no chest wall retraction.

	Introduction

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Since minimally invasive direct coronary artery bypass (MIDCAB) wasfirst reported by Benetti and colleagues ¹ in November 1995, the number of procedures performed has increasedexponentially. Variations of MIDCAB have been described, but the standardapproach involves dissection of the left internal thoracic artery (LITA) fromthe chest wall through a small left anterior thoracotomy, immobilization ofthe left anterior descending coronary artery (LAD) by a combination of mechanicalor pharmacologic means, and anastomosis of the end of the LITA to the sideof the LAD on the beating heart without cardiopulmonary bypass. MIDCAB advantagesinclude the avoidance of cardiopulmonary bypass morbidity and the economicadvantages of decreased resource use.

In our initial experience of 32 standard MIDCAB procedures, we routinelyobtained postoperative angiograms. Although the clinical results were good,a number of patients (11 of 32) had angiographic abnormalities, and a fewultimately required conventional bypass (2 of 32). Others ^2,3 have reportedsimilar experiences. In addition, our early MIDCAB patients experienced postoperativeincisional pain disproportionate to the length of their incision. The issueof a vigorously retracted anterior thoracotomy could not be disregarded.

On the basis of our consideration of these issues, we devised a noveltechnique for performing minimally invasive arterial bypass of the LAD.

	Methods

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Patient selection.
From December 1996 through March 1997, eight patients at the Beth IsraelDeaconess Medical Center gave informed consent before undergoing bypass graftingof their LAD with a 3 to 8 cm segment of right inferior epigastric artery(RIEA) attached proximally end-to-side to their in situ LITA. On the basisof the final configuration of this graft and its proximal and distal vessels,we termed this operation an "H" graft MIDCAB (HG-MIDCAB).

Two of these eight patients were women. The mean age was 63 years (range48 to 84 years). Five patients had unstable angina preoperatively and threehad positive exercise tolerance tests despite maximal medical therapy. Fourpatients had previously undergone catheter-based interventions. In five patients,LAD grafting constituted a complete revascularization. Three patients hadmultivessel disease but were believed to be prohibitively poor candidatesfor conventional coronary artery bypass grafting with cardiopulmonary bypass.

Description of the procedure.
The supine, anesthetized patient has a single-lumen endotracheal tubeplaced and a transesophageal echocardiographic probe passed. Swan-Ganz catheters(Baxter Healthcare Corp., Edwards Division, Santa Ana, Calif.) have not beenroutinely used.

Through a short thoracotomy (6 to 7 cm) over the fourth rib medial tothe left nipple, the pectoralis muscle is divided, and the exposed costalcartilage is removed by disarticulation at the chondrosternal joint. The LITAlies immediately deep to the cartilage such that a 1.5 to 2.0 cm segment ofvessel is thereby exposed. The musculophrenic, superior epigastric, and allintercostal branches are left intact because there is no dissection of theinternal thoracic artery from the thoracic wall.

While the thoracotomy is being performed, an assistant harvests theRIEA from the inferior abdominal wall. The artery and accompanying veins areharvested on a narrow pedicle. Generous papaverine irrigation is used to preventspasm. We initially used a 5 cm vertical right lower quadrant paramedian incision(five patients), but we have recently developed a technique for performinglaparoscopic harvest (three cases). A short segment of radial artery may beused as an alternative to the RIEA.

After exposure of the LITA and while the harvesting of the RIEA is beingcompleted, the pericardium is opened and the LAD is identified and immobilizedas has been described for standard MIDCAB. ¹ Systemic heparin is given to maintain the activated clotting timegreater than 300 seconds, and the flow through the LAD is temporarily stoppedusing silicone-elastic vessel loops proximal and distal to the point of anastomosis.Ischemic preconditioning was not used in this series. After proximal occlusion,the LAD is opened and the RIEA is sutured to the arteriotomy with running8-0 polypropylene. This step is facilitated by the short, untethered RIEA,which can be moved about to facilitate exposure of each aspect of the anastomosis.After completion of the anastomosis, LAD flow is restored, and the characterof back bleeding through the RIEA is noted. Thus a crude assessment of distalanastomotic patency intraoperatively is made possible. Brisk, pulsatile backflowsuggests a good anastomosis and is uniformly present despite a tight proximalLAD stenosis. In addition, a coronary probe can be passed down the RIEA acrossthe anastomosis, or a syringe and blunt needle can be attached to the freeend of the RIEA graft, permitting injection and resistance assessment. Noneof these intraoperative technical quality checks are possible with standardMIDCAB.

The RIEA is then measured to a point on the short segment of exposedLITA that will permit a straight path for the conduit. The graft may comeoff precisely at a right angle or have a slightly obtuse angle relative tothe proximal LITA. This direct measurement is performed during full volumeventilation and precludes the addition of any but the most minimal redundancyin length. The horizontal orientation of the graft reduces the risk of graftkinking caused by lung motion. The RIEA is trimmed to the desired length,after which an anastomosis is constructed between the proximal end and theside of the in situ LITA at the area exposed earlier. Local arterial controlis obtained with microvascular clamps on the RIEA and on the LITA proximaland distal to the point of anastomosis. After completion of the anastomosis,the clamps are removed and a Doppler flow probe is used to assess flow throughthe "H" segment. The wounds are closed and the patient is extubated.A small chest tube is used in patients in whom the left pleura is entered.

	Results

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Intraoperatively.
We have performed eight HG-MIDCAB operations as described above. AllRIEA conduits have been satisfactory for interposition as a coronary bypassgraft. Gross atherosclerosis has not been present in any RIEA. Lumen diameterhas ranged from 1.9 to 3.3 mm as determined by evaluation of digitized imagesobtained from the postoperative angiogram. The average graft length has been5.8 cm, with a range of 3.1 to 7.8 cm.

Mechanical immobilization has precluded the need for negative inotropesor rate-controlling drugs during anastomosis of the RIEA to LAD. In each case,brisk pulsatile back bleeding from the RIEA has been present after completionof the distal anastomosis. Rib retraction has not been necessary in any case.No patient has required institution of cardiopulmonary bypass or conversionto conventional coronary artery bypass graft through a median sternotomy.All patients but one have been extubated in the operating room.

Postoperatively.
All patients who had the operation for unstable symptoms had resolutionof those symptoms with the operation. No perioperative infarctions occurred,and no evidence of postoperative cardiac ischemia was present. No wound complicationsoccurred. Two patients experienced transient atrial fibrillation that respondedto procainamide. One patient, an 83-year-old man with chronic renal failure,had a massive upper gastrointestinal hemorrhage from a duodenal ulcer postoperativelyand required an urgent laparotomy, which he tolerated well. Although it wasour subjective impression that HG-MIDCAB patients had less pain than patientsin the prior experience who had traditional LITA dissection, a concurrentprospective, randomized pain study precluded comparing their respective analgesicrequirements.

The six patients with normal or near normal renal function underwentrepeat coronary angiogram on the first postoperative morning (Fig. 1). Acceptable graft lie without kinkingor arterial (RIEA, LAD, or LITA) irregularity was demonstrated in each case.Each study revealed prompt filling of the LAD through an RIEA graft caliberequal to or greater than the recipient vessel. Four of the eight patientshave undergone postoperative exercise thallium tests without evidence of LADterritory ischemia.

View larger version (98K): [in this window] [in a new window]   Figure 1. Postoperative angiogram demonstratinga widely patent right inferior epigastric (RIEA) "H" graft fromthe in situ left internal thoracic artery (LITA) to the left anterior descending(LAD) coronary artery.

	Discussion

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Although the intermediate and long-term patency of the inferior epigastricartery as an graft has not been demonstrated, favorable early results havebeen achieved using this conduit for aorta-coronary grafting. ^4,6 Furthermore,the short arterial segment required to construct an "H" graftallows the small distal RIEA to be discarded. Only the proximal half withits generous diameter, few branches, and LITA histologic similarities ⁷ is used. Although we have not hadany problems with the suprainguinal, paramedian skin incision, an alternativeto the RIEA might be a short segment of radial artery.

Perhaps the most intriguing possible disadvantage is the potential fordiversion of significant LITA flow to noncoronary vascular beds representingsome variant of a "steal" syndrome. Because the LITA is completelyin situ, distal flow through the intercostal arteries to the abdominal walland the diaphragm is maintained. It is not known whether these beds, underany circumstances, can divert LITA flow and decrease the amount of blood deliveredto the heart, nor is it known whether such a diversion of flow could be clinicallysignificant. In contrast to anecdotal published reports ^8,9 of patientswho were believed to have LAD territory ischemia resulting from intact, largeproximal LITA intercostal branches, other authors have demonstrated no distalflow deprivation with intact proximal intercostal branches. ¹⁰ Certainly our clinical results, including postoperativethallium stress tests obtained in four of the HG-MIDCAB patients, suggestthat graft flow insufficiency is not a clinical problem during exercise.

HG-MIDCAB, in contrast to the standard MIDCAB, requires less dissection,provides excellent visualization, permits better intraoperative assessmentof distal anastomotic patency, facilitates construction of a tension-freenonkinking graft, and is associated with less chest wall retraction. Our earlyexperience with this technique suggests that the "H" graft isan attractive alternative to standard MIDCAB, and, in view of its advantages,we are now using this modification as our minimally invasive coronary bypassgrafting procedure of choice.

	References

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