Effects of antecedent anginal episodes and coronary artery stenosis on left ventricular function during coronary occlusion

Protein-, gene-, and cell-based therapeutic angiogenesis for the treatment of myocardial ischemia

Therapeutic angiogenesis aims at restoring perfusion to chronically ischemic myocardial territories by using growth factors or cells, without intervening on the epicardial coronary arteries. Despite angiogenesis having received considerable scientific attention over the last decade, it has not yet been shown to provide clinical benefit and is still reserved for patients who have failed conventional therapies. Nevertheless, angiogenesis is a very potent physiologic process involved in the growth and development of every animal and human, and it is likely that its use for therapeutic purposes, once its underlying mechanistic basis is better understood, will one day become an important modality for patients with CAD and other types of organ ischemia. This review summarizes current knowledge in therapeutic angiogenesis research.

Angiogenic protein therapy

Therapeutic angiogenesis, in the form of growth factor protein administration or gene therapy, has emerged as a new method of treatment for patients with severe, inoperable coronary artery disease. Improved myocardial perfusion and function after the administration of angiogenic growth factors has been demonstrated in animal models of chronic myocardial ischemia. A recent clinical study reported beneficial long-term effects of therapeutic angiogenesis using FGF-2 protein in terms of freedom from angina and myocardial perfusion on nuclear imaging and suggested that protein angiogenic therapy has the potential to extend treatment options to patients who are not optimal candidates for conventional methods of myocardial revascularization. The ultimate role that angiogenesis will play in the treatment of ischemic heart disease will, however, be determined from adequately powered, randomized, double-blind, placebo-controlled trials. It is likely that endogenous antiangiogenic influences, intrinsic lack of response of patients with severe endothelial dysfunction, and other limitations will have to be overcome before angiogenesis becomes standard therapy for the treatment of coronary artery disease.

Gene transfer to induce angiogenesis in myocardial and limb ischaemia

Stimulation of angiogenesis/arteriogenesis by gene transfer methods offers hope for treating patients with myocardial and peripheral limb ischaemia who are not candidates for standard revascularisation procedures. Preclinical studies showed that adenoviral and plasmid vectors encoding various angiogenic cytokines were capable of inducing functionally significant angiogenesis in vitro and in animal models of chronic myocardial ischaemia. Early clinical studies using VEGF121-, FGF-4- and VEGF165-encoding vectors showed a reasonable safety profile with promising results. However, significant advances in vector technology including regulatable and longer-term expression, delivery strategies (local and organ/tissue specific), clinical trial design, and outcome measure development are needed before this investigational treatment becomes reality.

Gene transfer for angiogenesis in coronary artery disease

Angiogenesis is a promising novel therapeutic strategy to provide new venues for blood flow in patients with severe ischemic heart and peripheral vascular disease, who are not candidates for standard revascularization strategies. We describe the underlying mechanisms involved in physiologic and therapeutic angiogenesis, underscoring the relative importance of vasculogenesis, angiogenesis, and arteriogenesis. We then present the various gene transfer vectors including plasmid, viral, and cell-based vectors, and various delivery modalities. The available preclinical data are presented, followed by a description of preliminary clinical experience, with an emphasis on the preliminary nature of these results, which address safety and not efficacy. Finally, we discuss the promises and pitfalls of clinical angiogenesis and gene transfer studies, stressing the importance of proper design of clinical trials and adequate protection of research subjects.

Continuous monitoring of global left ventricular ejection fraction during percutaneous transluminal coronary angioplasty

Continuous monitoring of left ventricular (LV) function during percutaneous transluminal coronary angioplasty (PTCA) was performed in 40 patients (53 +/- 2 years) with a miniature, nuclear detector system after labeling the patients' red blood cells with technetium-99m. Balloon dilation (113 seconds, range 60 to 240) induced on average a 0.12 ejection fraction (EF) unit (19%) decrease in the LVEF, which was explained by a 34% increase in end-systolic counts. Balloon dilation of the left anterior descending artery (n = 23) produced a decrease in the LVEF of 0.17 +/- 0.13 EF units compared with the decrease of 0.06 +/- 0.07 EF units in patients undergoing dilation of the left circumflex artery (n = 9) and 0.05 +/- 0.04 EF units in patients treated for a stenosis of the right coronary artery (n = 8), (p = 0.02). Balloon deflation was associated with an immediate return to pre-PTCA levels. In 10 patients with 2 identical balloon occlusions, the second occlusion led to a significantly less decrease in the LVEF (0.41 +/- 0.14 vs 0.44 +/- 0.15) and electrocardiographic ST-segment deviation (88 +/- 54 microV vs 65 +/- 42 microV) than the first. We conclude that PTCA is associated with an abrupt transient decrease in the LVEF. The effect of balloon occlusion of the left anterior descending artery is more pronounced than balloon occlusion of the left circumflex and the right coronary arteries. Neither single nor multiple balloon occlusions were associated with post-PTCA global LV dysfunction, whereas the lesser degree of LV dysfunction and electrocardiographic signs of myocardial ischemia during the second of 2 identical balloon occlusions suggests that preconditioning can be induced during PTCA.