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New Developments in Cardiovascular Medicine for the Elderly

Steven N. Konstadt, M.D.

Mount Sinai School of Medicine

As the population ages, physicians are required to treat more patients with advanced cardiovascular disease. Fortunately, medical science continues to make new advances that facilitate this treatment. These new advances take the many forms:

Many of these new interventions provide less invasive alternatives to procedures that they replace. This talk will highlight some of these new advances

Minimally Invasive Cardiac Surgery:

There are several key factors driving the development of minimally invasive cardiac surgery:

Cost Containment:

Until the early 1990's most patients were covered by indemnity insurance plans and there was little incentive to reduce costs. Then managed care became more popular, and new government cost cutting initiatives were launched. Reduced fee for service rates, global pricing for cardiac surgery and capitation created tremendous cost containment pressures. The initial response of the health care providers was to reduce their charges to maintain market share. This was done without clear analysis of their cost of providing the services, and in some cases the procedures were performed at a loss. Small changes in surgical procedure, anesthetic management, and nursing care were able to slightly reduce the cost of delivering the care, but these incremental savings were not sufficient to match the drastic cuts in reimbursement. Clearly a quantum improvement was needed. Detailed cost analysis and discounted cash flow projections are needed to document actual savings created by minimally invasive surgery.

Patient Satisfaction:

In other surgical specialties, more and more procedures were being performed by minimally invasive techniques, this put pressure on cardiac surgery to match these developments. Similarly cardiac surgery had to match the improvements in interventional cardiology (e.g. stents, radiation, atherectomy, and angiogenesis).

Competitive Advantage:

Offering new and unique surgical procedures (e.g. port-access and off-pump CABG) allowed tertiary care facilities to differentiate themselves from community hospitals and attract more patients.

CQI/Scientific Improvement:

New quality improvement initiatives in medicine lead to re-thinking the entire surgical process. This lead to new solutions that included port access and off pump surgery.

Entrepreneurial Opportunity:

Decreased reimbursement for services lead physicians to seek other applications of their intellectual property. In the rapid economic expansion of the 1990's seed capital available for biotech developments was readily available. Industry also recognized the opportunity to create new, patented technology in for a huge healthcare market.

Patient Demographics:

With the aging of the population and the delay of surgery by interventional cardiology, patients undergoing cardiac surgery are now older and sicker than ever before. This older population is at greater risk of developing a perioperative stroke. Though large studies are needed to clearly prove this idea, it seems that off-pump CABG may pose a lower risk of post-operative neurologic deficit

Endovascular Aortic Surgery

Endovascular aortic repair is a new alternative to conventional surgical repair of aortic pathology.1) This technique of aortic repair was first suggested by Dotter in 1969 and reached clinical application with the work of Parodi et al in 1990.2,3) Since this early work, the technology has been applied to the treatment of peripheral artery aneurysms,4,5) diffuse aorto-iliac occlusive disease,6) aortic aneurysms, pseudoaneurysms (Figure 1), and dissections, coarctation of the aorta (Figure 2), and traumatic aortic or arterial injuries.7) Endovascular grafts have the distinct advantage of being a less invasive technique compared with conventional arterial reconstructions, owing to the unique ability to insert these grafts through a small incision from remote arterial access sites. This minimally invasive approach results in several advantages to the patient compared with conventional aortic repair. Many patients undergoing aortic repair have concomitant cardiac, renal, and pulmonary disease, increasing the complexity of any anesthetic administered. Avoiding laparotomy or thoracotomy eliminates the need for extensive perioperative aortic dissection, which may be complicated by previous aortic surgery. This technique obviates the need for extensive and prolonged aortic occlusion, decreases blood loss, and avoids the significant fluid shirts that occur with visceral manipulation, thus lowering the risk of significant hemodynamic changes perioperatively. Conventional open aortic repair required general anesthesia with or without supplemental regional anesthesia. The repair via the endovascular route is a less invasive technique compared with an open reconstruction.8)

Endovascular aortic repair is a minimally invasive procedure, which may offer many advantages over conventional open aortic repair. Immediate technical success can be achieved in at least 80-90% of patients presenting for endovascular aortic aneurysm repair. The perioperative mortality is most likely less than conventional surgical repair. Although these procedures are less invasive, complications still arise; these complications tend to be local and vascular (hence easily treatable) as opposed to the systemic complications seen after open repair. Because this technique is still in its infancy, the long-term results have not yet been well described. Since arterial rupture is a recognized risk of this procedure, appropriate facilities must be present for resuscitation. In addition to helping to delineate the aortic pathology, TEE may provide valuable information about the surgical results. Future studies, especially on outcomes, will direct people for the proper treatment of aortic aneurysms.

Valve repair

Though valve repair is not new, it is becoming increasing popular. It is also being performed in a broader range of valvular abnormalities. Though these procedures require specialized surgical and anesthetic management, there are numerous advantages to repair over replacement. These advantages are summarized below

Non-Surgical Approaches to Revascularization

Until the early 1970's, coronary artery was only treated by drugs (with minimal success), then Coronary Artery Bypass Grafting (CABG or Bypass surgery) was introduced. About ten years later, a less invasive method to relieve the blockages in the coronary arteries was introduced. This technique is called Percutaneous Transluminal Coronary Angioplasty (PTCA, or more simply angioplasty). PTCA involves inflating a balloon across the blockage (lesion) in the artery, thereby dilating the diseased vessel and restoring blood flow to the myocardium. Despite twenty years of advances in PTCA techniques, a high percentage (40%) of patients develop recurrence of the blockage within a very short time. This problem is called restenosis and it remains the critical limiting factor of PTCA. This restenosis is a maladaptive process that occurs secondary to a complex cascade of events, which are touched off by vascular injury to the coronary arteries.

Currently the most common means to treat or prevent restenosis is to place a stent at the site of the blockage. The stent is designed to hold the vessel open. Though stents can be helpful, they are not a perfect solution to the clinical problem. Placing a foreign body in the vessel can induce more injury or lead to blood clotting. More recently, scientists have gained a better understanding of the basic molecular and biologic phenomena in the vascular injury and repair that lead to restenosis. Although the exact mechanism is unknown, several factors may enhance smooth muscle cell growth and therefore may play a role in the development of restenosis. These include cell (platelet) deposition, mechanical stretching, inflammation of the vessel wall, the activity of growth factors, and alterations in vessel geometry.

The possible mechanisms of restenosis suggest several potential ways to limit the proliferative response to vascular injury. Such approaches include blood thinners (anticoagulants and platelet antagonists), direct inhibitors of smooth muscle proliferation, anti-inflammatory agents, and growth factor inhibitors. Energy-based approaches, including the use of radiation and laser technology, have been shown recently to have promise. Additionally, devices, which improve final vessel geometry, are currently being tested as methods to curb restenosis. Finally, genetic approaches have now entered into the research arena. It has been shown recently that patients with a variant of the gene that encodes angiotensin-converting enzyme (ACE) are up to four times more likely to develop restenosis after angioplasty. Below is a more detailed discussion of the different treatment approaches.

Treatment Options:

Currently there are four major categories of treatment to reduce restenosis. They are as follows:

(1) Pharmacological: These therapies involve interfering with platelet function so that the risk of clot formation is significantly reduced. Other new drugs may include antibiotics and anti-inflammatory agents.
(2) Mechanical: Mechanical interventions include stents, atherectomy, and extraction. As stated above, the coronary stent has been found to partially answer the restenosis problem. Artherectomy is another procedure that involves the mechanical removal of the blockage. It can be performed using either a small laser to vaporize the blockage, a small knife to cut it away or a small burr to smooth the lining of the blood vessel. The risks of these procedures are similar to those for the stent procedure.
(3) Radiation: A new approach to the management of restenosis involves applying radiation to the diseased segment of the coronary artery. This can be accomplished by making the stents radioactive, or through a catheter. Two different types of radiation are used: beta and gamma. Logistically, beta radiation is easier to use. The small doses of radiation are believed to inhibit the formation of new cells, and thus prevent restenosis. Very little clinical data is available to evaluate this therapy.
(4) Angiogenesis: Angiogenesis means forming new blood vessels to replace the diseased vessels. One way to accomplish this is by gene therapy. This technology involves using foreign DNA in order to stimulate the growth of new blood vessels, which will be able to circumvent the diseased ones. This can be accomplished by direct injection into the coronary arteries, intravenous injection, and intramyocardial injection. Some initial studies suggest that intracoronary injection may improve perfusion defects and myocardial contractility.A second technique to stimulate new vessels is to burn a small hole in the heart muscle with a special laser. This approach can be performed through three routes: intraoperative transmyocardial revascularization (ITMR), percutaneous myocardial revascularization (PMR), and thoracoscopic transmyocardial revascularization (TTMR). These approaches allow physicians to create channels both from the inside of the heart (PMR-endocardial approach) outward through part of the myocardium (heart muscle) and from the outer surface of the heart (ITMR & TTMR-epicardial approach) inward toward the ventricular cavity. TMR can be used by cardiovascular surgeons as a sole therapy or as a therapy used in combination with other revascularization procedures (such as coronary bypass grafting-CABG or percutaneous transluminal angioplasty-PTCA). Initial studies have shown that laser angiogenesis can relieve symptoms and may improve exercise tolerance.

1) Dake MD, Miller DC, Semba CP, et al. Transluminal placement of endovascular stent-grafts for the treatment of descending thoracic aortic aneurysms. N Engl J Med 1994; 331:1729-1734.
2) Dotter CT. Transluminally-Placed coilspring endarterial tube grafts: Long term patency in canine popliteal artery. Invest Radiol 1969:4:329-332.
3) Parodi JC, Palmaz JC, Barone ND. Transfemoral intraluminal graft implantation for abdominal aortic aneurysms. Ann Vasc Surg 1991; 5:491-499.
4) Marin ML, Veith FS, Panetta TF. Transfemoral endoluminal stent graft repair of a popliteal artery aneurysm. J Vasc Surg 1994; 19:754-757.
5) Marin ML, Veith FJ, Lyon RT, et al. Transfemoral endovascular repair of iliac artery aneurysm. Am J. Surg 1995; 170:179-182.
6) Marin ML, Veith FJ, Sanchez LA, et al. Endovascular aortoiliac grafts in combination with standard infrainguinal arterial bypasses in the management of limb-threatening ischemia. J Vasc Surg 1995; 22:316-322.
7)Marin ML, Veith FJ, Panettta TP, et al. Transluminally placed endovascular stented grafts for repair of arterial trauma. J Vasc Surg 1994; 20:466-473.
8) Swartbol P, Truedsson L, Norgren L. The inflammatory response and its consequence for the clinical outcome following aortic aneurysm repair. Eur J Vasc Endovasc Surg 2001 May;21:393-400