Ann Thorac Surg 2006;81:e21-e23
© 2006 The Society of Thoracic Surgeons
How to do it
Rapid Ventricular Pacing to Lower Blood Pressure During Endograft Deployment in the Thoracic Aorta
Suwatchai Pornratanarangsi, MD,
Mark W.I. Webster, MB, ChB
*
,
Peter Alison, MB, ChB,
Parma Nand, MB, ChB
Green Lane Cardiovascular and Cardiothoracic Surgery Units, Auckland City Hospital, Auckland, New Zealand
Accepted for publication January 23, 2006.
* Address correspondence to Dr Webster, Green Lane Cardiovascular Service, Auckland City Hospital, Private Bag 92 024, Auckland, 1001 New Zealand (Email: mwebster{at}adhb.govt.nz).
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Abstract
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Controlled hypotension is critical to the accurate deployment of aortic endografts and safe balloon post-dilation. We describe the use of rapid ventricular pacing during 15 aortic stenting procedures. An immediate and sustained reduction in both phasic and mean blood pressure was achieved in all patients. This procedure has advantages over pharmacologic or other methods of blood pressure reduction.
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Introduction
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Endovascular stent grafting is an accepted treatment for many patients with abdominal and thoracic aortic aneurysms, and in some patients with type B aortic dissection [1, 2]. In the thoracic aorta, aneurysms and dissections often arise close to the left subclavian artery; procedural success frequently depends on exact positioning of the proximal end of the stent. Inaccurate positioning of a stent graft may compromise cerebral perfusion or may predispose the patient to post-deployment endoleaks, which have been reported in as many as 32% of patients [1, 2]. Positioning of the stent graft is made difficult by pulsatile aortic blood flow causing a to-and-fro motion, and by proximal hypertension, which rapidly develops with partial stent graft deployment and exerts a force tending to move the stent graft distally.
Several techniques have been proposed to overcome this problem including pharmacological-induced hypotension or transient cardiac asystole [3–5], and balloon occlusion of the aorta or vena cava [6]. Each has its advantages and disadvantages. We describe the use of rapid transvenous cardiac pacing to control blood pressure during stent graft positioning and deployment.
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Technique
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Rapid ventricular pacing was introduced in March 2004. Since then we have undertaken 15 consecutive endovascular stent grafting procedures of the descending thoracic aorta using 29 endoprostheses, mostly the self-expandable Talent graft (Medtronic Vascular, Santa Rosa, CA), and more recently the Valiant (Medtronic Vascular) and Zenith (Cook Inc, Bloomington, IN) grafts (4 each). Endograft prosthesis specifications and implant strategy were predetermined from 3-mm slice computed tomographic aortograms, generally with three-dimensional reconstruction, confirmed with the procedural aortogram. The indication for stenting was aortic aneurysm (7 patients), type B aortic dissection (2 patients), aortic transection (4 patients), penetrating ulcers (1 patient), and aortobronchial fistula (1 patient). The patients ranged in age from 21 to 80 years, with 12 who were males. All patients gave written informed consent. All procedures were performed under general anesthesia in the cardiovascular catheterization laboratories under angiographic guidance.
A 6-French pigtail was advanced from the left brachial artery to the ascending aorta to monitor systemic pressure, perform initial aortography, and act as a useful landmark for the left subclavian artery. All patients received 5,000 units of heparin. A 5-French bi-polar or quad-polar cardiac pacing wire was positioned in the right ventricular apex through the right femoral vein. Once in position, the pacing threshold was checked; an acceptable threshold was less than 1 mV. The pacemaker output was set to 5 mV, and pacing was performed at rates of 130 to 180 beats per minute, adjusted to lower the systolic pressure to 50 to 60 mmHg. The right common femoral artery was exposed surgically for endoprosthesis delivery, which was facilitated by advancing the device over a super stiff Amplatz 0.035 inch x 300 cm guidewire (Cook Inc) under fluoroscopic guidance.
Just before deployment, rapid ventricular pacing was activated. Pacing was repeated during deployment of additional stents, and was also utilized during post-deployment ballooning, a time when hypertension is especially pronounced.
This maneuver immediately and markedly reduced systolic blood pressure, with the effect lasting for the duration of stent deployment (Fig 1). The blood pressure almost immediately returned to normal after inactivation of the pacemaker. There was no distal stent dislodgement during deployment or ballooning under rapid pacing, and there were no pacing-related complications.
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Fig 1. (A) Immediate reduction in phasic and mean blood pressure with pacing at 130 beats per minute. (B) Almost immediate return of blood pressure after inactivation of the pacemaker.
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Comment
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The ability to achieve controlled blood pressure reduction is critical during endograft prosthesis treatment of thoracic aortic pathology. This reduction must be maintained during the deployment phase of the device and during any subsequent ballooning of the endoprosthesis. We demonstrate a safe and easy method of reducing both the phasic and mean blood pressure. A particular attraction of this method is the near immediate onset and offset of action. In addition, the pacing rate can be readily adjusted to titrate the desired blood pressure reduction.
The problem of stent graft movement caused by pulsatile aortic blood flow has been recognized since the early studies of endovascular stent grafting. While optimizing device stability prior to deployment (such as using an extra stiff guidewire), and deploying rapidly to minimize the time for aortic pressure to increase with a partially-deployed stent, may reduce the likelihood of distal stent displacement, controlled hypotension at the time of stent deployment is key to exact positioning of the endovascular stent graft.
A number of other approaches to blood pressure reduction have been reported. Pharmacological-induced systemic hypotension, most commonly using nitroglycerin, sodium nitroprusside, or short-acting beta-blockers, can lower the mean arterial pressure to 50 mm Hg for 1 to 4 minutes [3], but this requires dose titration and has a considerably slower onset and offset of action than pacing. Another pharmacological method of pressure reduction is transient (usually 10 to 30 seconds), cardiac asystole induced by intravenous adenosine administration [4, 5]. The Valsalva maneuver has been used, as has the induction of transient ventricular fibrillation [7].
Proximal aortic balloon occlusion effectively diminishes flow, but at the expense of greatly increased cardiac afterload with the potential for aortic or cardiac injury. The large occlusion balloon needs a large sheath through the brachial artery and a segment of normal aorta proximal to the lesion. Temporary vena caval balloon occlusion has also been reported [6], using an occluding balloon inflated with diluted contrast or carbon dioxide. Possible complications of this technique include balloon rupture or migration and intracranial venous hypertension, particularly when the superior vena cava is occluded.
Temporary transvenous cardiac pacing is widely used for treating bradyarrhythmias. Rapid ventricular pacing is used during electrophysiology studies to evaluate and terminate ventricular tachyarrhythmias. Ventricular pacing at a rate of 130 to180 beats per minute reduces mean arterial pressure to 40 to 60 mm Hg. The mechanisms involve loss of atrioventricular synchrony and reduction of ventricular filling time, resulting in decreased left ventricular preload, stroke volume, and cardiac output. Hypotension induced by preload reduction seems to cause less cardiac and aortic stress than other methods. It is well tolerated by the patient and readily undertaken in patients under local anesthesia.
Serious complications associated with temporary cardiac pacing of short duration are rare [8]. We observed none in our series. In the absence of prior ventricular tachycardia, the risk of entraining a ventricular tachyarrhythmia is likely less than 1%, and overdrive pacing or cardioversion may be needed in such circumstances. There is a small risk of right atrial appendage or ventricular perforation, requiring pericardiocentesis or surgical repair. In patients with pre-existing left bundle branch block, there is also a small chance of the patient becoming temporarily pacemaker-dependent.
In summary, temporary rapid ventricular pacing is a safe, simple, predictable, and effective method of inducing sustained hypotension, enabling precise deployment of endovascular stent grafts and safe post-stent ballooning. It seems better than many other approaches that have been used, particularly with regard to the rapid onset and offset of effect.
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References
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- Farber MA, Criado FJ. Endovascular repair of nontraumatic ruptured thoracic aortic pathologies Ann Vasc Surg 2005;19:167-171.[Medline]
- Leurs LJ, Bell R, Degrieck Y, Thomas S, Hobo R, Lundbom J, EUROSTAR. UK Thoracic Endograft Registry collaborators Endovascular treatment of thoracic aortic diseasescombined experience from the EUROSTAR and United Kingdom Thoracic Endograft registries. J Vasc Surg 2004;40:670-679.[Medline]
- Bernard EO, Schmid ER, Lachat ML, Germann RC. Nitroglycerin to control blood pressure during endovascular stent grafting of descending thoracic aortic aneurysms J Vasc Surg 2000;31:790-793.[Medline]
- Dorros G, Cohn JM. Adenosine-induced transient cardiac asystole enhances precise deployment of stent-grafts in the thoracic or abdominal aorta J Endovasc Surg 1996;3:270-272.[Medline]
- Kahn RA, Moskowitz DM, Marin ML, et al. Safety and efficacy of high dose adenosine-induced asystole during endovascular repair J Endovasc Ther 2000;7:292-296.[Medline]
- Ishiguchi T, Nishikimi N, Usui A, et al. Endovascular stent-graft deploymentTemporary vena caval occlusion with balloons to control aortic blood flow- experimental canine study and initial clinical experience. Radiology 2000;215:594-599.[Abstract/Free Full Text]
- Kahn RA, Marin ML, Hollier L, Parsons R, Griepp R. Induction of ventricular fibrillation to facilitate endovascular stent graft repair of thoracic aortic aneurysms Anesthesiology 1998;88:534-536.[Medline]
- Murphy JJ. Current practicecomplications of temporary transvenous cardiac pacing. BMJ 1996;312:1134.[Free Full Text]
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Abstract
Introduction
