Donor heart

The shortage of donor hearts has prompted development of new surgical techniques, including ventricular aneurysm resection, mitral valve repair, and myocardial cell transplantation, which have resulted in variable degrees of symptomatic improvement. 

The initial generation of mechanical pumps was used to stabilize patients until a donor heart becomes available. In 2001, the REMATCH trial demonstrated the use of LVADs as destination therapy in patients with heart failure ineligible for transplantation [19]. In a minority of patients, the pumps are used as bridge to recovery [17]. 

Figure 9.1 In this heart transplant, a surgeon holds the donor heart as a colleague prepares to connect its blood vessels to the blood vessels of the recipient.

Alprostadil is PGEi available for exogenous administration. Alprostadil is widely used in neonates with cyanotic congenital heart disease to maintain the patency of the ductus arteriosus. Reported adverse effects include fever, apnea, flushing, bradycardia, and hyperostosis. Continuous chronic infusion of alprostadil via a portable pump and neuromuscular electrical stimulation help to improve the quality of life in patients with severe chronic heart failure waiting for a donor heart, as both treatments can be performed at home. 

Jayakumar, J., Suzuki, K., Khan, M., Smolenski, R.T., Farrell, A., Latif, N. et al. (2000) Gene therapy for myocardial protection Transfection of donor hearts with heat shock protein 70 gene protects cardiac function against ischemia-reperfiision injury. Circulation, 102 (19 Suppl. 3), III302-306. 

Figure I /./ Loewi s demonstration of the chemical nature of neurotransmission. Heart D (donor) represents heart 1 while heart R (recipient) represents heart 2. Tracings R and D represent the respective heart beats of the two hearts. When fluid from the stimulated donor heart was allowed to interact with the recipient heart (middle of tracing R), heart rate was obviously abbreviated.

This concept has enormous implications in the setting of cardiac surgery and heart transplantation [11-13]. Conditions of ischemia and reperfusion are created routinely by the surgeon during open heart procedures, i.e., cardiopulmonary bypass and aortic cross-clamping [11,12], Similar conditions prevail during heart transplantation when the ischemic donor heart is rapidly reoxygenated by the recipient s blood [14]. 

Potential cardiovascular therapeutic uses for PFC emulsions, other than CPB, include treatment of acute myocardial infarction, cardioplegia, reperfusion, coronary angioplasty and preservation of donor hearts for transplantation. High 02-delivery capacity, small particle sizes, and low viscosity may improve tissue perfusion and oxygenation. Treatment of cardiac arrest is also being explored. 

In the course of their work on a canine heart model for angina, Szentivanyi and co-workers claim to have found evidence for the existence of a substance, hyperemin, which regulates coronary vessel responsiveness to metabolic requirements. In the absence of hyperemin, vasodilation could no longer be produced by metabolic stimuli or by adrenalin. Administration of hyperemin from a donor heart reestablished normal responses. -Presumably, angina pectoris may involve a lack or insufficiency of a hyperemin type material in the human heart. 

Heart transplantation is usually an orthotopic procedure. Leaving most of the atria and septum of the recipient, the patient is placed on cardiopulmonary bypass. The donor heart is implanted by anastamosis of the left atrium to the residual left atrial wall and joining the right atrial wall and septum. The main pulmonary artery is connected to the ascending aorta."... 

Treatment strategies for progressive pulmonary venous hypertension should focus on treatment of the underlying disease. For patients with advanced decompensated systolic heart failure and secondary pulmonary hypertension, it is essential to reduce the pulmonary vascular resistance prior to heart transplantation to prevent acute RV failure of the donor heart. The use of continuous milrinone, occasionally nesirit-ide, and earlier intervention with mechanical circulatory device support (19) as a bridge to cardiac transplantation is considered a standard approach for this group of patients. Earlier intervention with valve repair or replacement for patients with mitral valve disease and aortic valve disease with associated pulmonary hypertension is recommended. 

Total Artificial Heart. Although heart transplants have been performed since the pioneering work of Christian Barnard in 1967, this procedure always requires a donor heart, which may not always be available. In addition, the body does tend to reject any implanted organs as undesired foreign material, and close matching of the tissues is difficult at the best. Although various immunosuppressant drugs can minimize this problem, the patient becomes more susceptible to infectious disease. A total artificial heart (TAH) would offer at least a partial answer to both of these problems. 

The indications for implantation of TAHs and VADs are similar to those for the lABP. but are usually reserved for patients who have failed balloon pump support and/or maximal medical therapy. Current FDA-approved VADs are placed for postcardiotomy support or as a bridge to either transplantation or recovery (Willman et al., 1999). Investigators are also evaluating chronic mechanical circulatory support as an alternative to transplantation for patients who do not meet the criteria to become a donor heart recipient (Rose et al., 1999). 

A modern version of the Jarvik-7 total artificial heart has been implanted in more than eight hundred people since 1982 but each device was removed when a donor heart became available. 

Heart Replacement and Repairs The term cardiovascular pertains to the heart, blood, and blood vessels. The heart is, of course, an absolutely essential organ. Aheart tiiat fails completely may be replaced by a donor organ. About 60,000 people suffer terminal heart failure each year in the United States, yet only about2500 donor hearts become available for transplant. Many attempts have been made— and continue to be made— to produce an artificial heart that can serve over a long period of time as a replacement for the natural organ. We will not devote attention to these efforts, except to note that recent results are quite promising. 

A. Ardehali, A. Fyfe, H. Laks, D. C. Drinkwater, Jr., J. H. Qiao and A. J. Lusis, Direct gene transfer into donor hearts at the time of harvest. /. Thorac. Cardiovasc. Surg., 109, 716-719 discussion, 719-720 (1995). 

Cardiac transplantation is the ultimate therapeutic option in end-stage CHF. Orthotopic cardiac transplantation is the surgical technique of choice, whereas heterotopic cardiac transplantation is performed primarily when there is high resistance in the pulmonary circulation of the recipient (and a heart-lung transplantation is impossible), the donor heart is too small, or in selected cases with acute but potentially reversible heart failure. In orthotopic transplantation the donor heart is joined to the recipients atria, aorta, and pulmonary artery. In heterotopic transplantation, the donor heart is implanted into the right thoracic cavity and anastomosed with the recipient s heart in a complex maimer in such a way that the donor heart takes over most of left ventricular output, while the recipient s heart continues to ensure right ventricular output. 

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