Persistent Proarrhythmic Neural Remodeling Despite Recovery From Premature Ventricular Contraction-Induced Cardiomyopathy.

Background: The presence and significance of neural remodeling in premature ventricular contraction-induced cardiomyopathy (PVC-CM) remain unknown.

Objectives: This study aimed to characterize cardiac sympathovagal balance and proarrhythmia in a canine model of PVC-CM.

Methods: In 12 canines, the investigators implanted epicardial pacemakers and radiotelemetry units to record cardiac rhythm and nerve activity (NA) from the left stellate ganglion (SNA), left cardiac vagus (VNA), and arterial blood pressure.

Left ventricular systolic dysfunction induced by ventricular ectopy: a novel model for premature ventricular contraction-induced cardiomyopathy.

Background: Premature ventricular contractions (PVCs) commonly coexist with cardiomyopathy. Recently, PVCs have been identified as a possible cause of cardiomyopathy. We developed a PVC-induced cardiomyopathy animal model using a novel premature pacing algorithm to assess timeframe and reversibility of this cardiomyopathy and examine the associated histopathologic abnormalities.

Aspirin desensitization/challenge in 3 patients with unstable angina.

Aspirin sensitivity is relatively frequent and can be a major problem in patients who need percutaneous coronary intervention and stenting with subsequent dual antiplatelet therapy. Desensitization is often the therapy in these patients, but this can prolong the time to revascularization significantly. Rapid oral aspirin desensitization protocols have been described since 2000.

Aortic baroreceptor function and depressed baroreflex sensitivity following myocardial infarction.

Depressed sinoaortic baroreflex control of heart rate following myocardial infarction (MI) is associated with increased morbidity and mortality. The etiology of this autonomic disturbance is unknown but could potentially occur at several levels of the reflex arc. The purpose of this study was to assess whether depressed baroreflex sensitivity (BRS) post-MI is associated with aortic baroreceptor dysfunction.

Reflex control of sympathetic outflow and depressed baroreflex sensitivity following myocardial infarction.

Reflex control of heart rate is frequently impaired following myocardial infarction. This is referred to as depressed baroreflex sensitivity. The aim of these experiments was to assess the function of other autonomic reflexes in dogs with depressed baroreflex sensitivity.

Failure of chronic transmyocardial laser revascularization to alter cardiac nociceptive reflexes: implications for the treatment of angina pectoris.

The aim of this study was to assess the delayed effects of transmyocardial laser revascularization (TMLR) on cardiac nociceptors. Experiments were performed in anesthetized dogs 1 month after thoracotomy with either TMLR (n = 17) or sham laser procedure (n = 17). All dogs underwent sinoaortic denervation and vagotomy to isolate the sympathetic afferent system.

Ventricular reflex interactions during transmural myocardial ischemia.

The role of left ventricular receptors with sympathetic afferent fibers in the reflex response to myocardial ischemia is controversial, particularly in the canine model. Previous experiments have shown that reflex excitatory responses mediated by left ventricular sympathetic afferents can be detected in sinoaortic denervated and vagotomized dogs during transmural myocardial ischemia. The purpose of these experiments was to determine if reflex excitatory responses occur in dogs with intact left ventricular vagal afferents.

Regional left ventricular deafferentation increases baroreflex sensitivity following myocardial infarction.

Objective: Depressed baroreflex sensitivity (BRS) has been observed following MI and has adverse prognostic implications. The mechanism for this finding is unknown. We tested the hypothesis that depressed BRS following myocardial infarction (MI) is related to augmented input from afferent receptors in the left ventricle.

Comparison of effectiveness of excimer laser angioplasty in patients with acute coronary syndromes in those with versus those without normal left ventricular function.

Depressed left ventricular (LV) ejection fraction (EF) adversely affects procedural outcome during percutaneous coronary revascularization. This study examined the acute results, effectiveness, and safety of excimer laser coronary angioplasty (ELCA) in patients with acute coronary ischemic syndromes whose LVEF was depressed (<40%) versus those with preserved LVEF. One hundred patients with acute coronary syndromes (51 with unstable angina and 49 with acute myocardial infarction) underwent ELCA.

Patients with coronary artery disease who present with chest pain have significantly elevated platelet contractile force and clot elastic modulus.

Rapid laboratory markers that correlate with patient risk would facilitate the decision making regarding admission of patients with chest pain (CP). Platelet contractile force (PCF) and clot elastic modulus (CEM) are elevated in patients undergoing coronary bypass grafting. This study assessed PCF, CEM, and platelet aggregation in patients presenting to the emergency department with chest pain (CP).

Relationship between dobutamine-induced regional wall motion abnormalities and coronary flow reserve in heart transplant patients without angiographic coronary artery disease.

Background: Regional wall motion abnormalities (RWMA) demonstrated by dobutamine stress echocardiography (DSE) are a sensitive predictor of coronary artery disease (CAD) in heart transplant recipients. However, RWMA have been shown to occur in patients with angiographically "normal" coronary arteries. The reasons for this are unknown.

Alterations of platelet aggregation kinetics with ultraviolet laser emission: the "stunned platelet" phenomenon.

Platelets, a major constituent of thrombus, play a crucial role in the pathogenesis of acute ischemic coronary syndromes. The effect of ultraviolet laser emission on platelets within thrombi is unknown. The effects of increasing levels of laser energy on platelets in whole blood were investigated.

In vivo effect of coronary laser angioplasty on atherosclerotic plaques: histopathologic analysis.

Information from histopathologic examination of coronary arterial atherosclerotic plaques treated with in vivo laser energy is sparse. Directional atherectomy provides biopsies for study of tissue changes (injury) due to coronary arterial debulking devices, including laser. Sixteen patients who presented with acute ischemic coronary syndromes underwent debulking of a total of 17 obstructive intracoronary lesions with pulsed-wave holmium:YAG laser (2.

Cardiac nociceptive reflexes after transmyocardial laser revascularization: implications for the neural hypothesis of angina relief.

Objective: The mechanism by which transmyocardial laser revascularization relieves angina is not understood. One theory is that laser-induced thermal damage to cardiac nerves results in cardiac denervation. This study examined the acute effects of transmyocardial laser revascularization on reflex responses mediated by cardiac nociceptors, the left ventricular receptors with sympathetic afferent fibers that are thought to mediate anginal chest pain.

Enhancement of t-PA Induced Fibrinolysis with Laser Energy: In-Vitro Observations.

The solid-state, pulsed-wave, holmium:YAG laser operates within strong water absorption peaks at the mid-infrared optical wavelength. This laser has been shown to be capable of inducing a mechanical, photoacoustic dissolution of fibrin, a major constituent of thrombi. It is not known whether this laser's energy combined with pharmacologic therapy can enhance the rate of fibrinolysis.

Vagal cardiopulmonary reflexes after total cardiac deafferentation.

Background: There are conflicting data regarding whether the primary source of afferent input for the vagal cardiopulmonary reflex emanates from receptors located in the ventricles, atria, and/or lungs. This study evaluated the effects of total cardiac deafferentation on the reflex control of efferent renal sympathetic nerve activity (RSNA) in response to a stimulus that affected all vagal receptors in the cardiopulmonary region.

Methods And Results: Experiments were performed in 14 chloralose-anesthetized dogs with sinoaortic denervation.

Absence of parasympathetic control of heart rate after human orthotopic cardiac transplantation.

Background: Partial reinnervation of cardiac sympathetic nerves has been observed after heart transplantation; we hypothesized that parasympathetic control to the heart after transplantation may return as well. To test this hypothesis, we examined heart rate responses produced by two cardiovascular reflexes whose efferent limbs are subserved by vagal fibers to the heart: (1) trigeminal reflex (simulated diving reflex) and (2) arterial baroreflex with phenylephrine injection.

Methods And Results: An "early" group (n=31, <24 months after transplantation) and a "late group" (n=27, >45 months after transplantation) were studied and compared with a control group with intact cardiac innervation (n=32) and a renal transplant group with similar transplant immunosuppressive regimen (n=11).

Simultaneous cardiac and renal sympathetic neural responses to activation of left ventricular sympathetic afferents.

In separate sets of experiments, we observed that activation of left ventricular sympathetic afferents by transmural myocardial ischemia (TMI) appeared to elicit greater reflex increases in efferent sympathetic nerve activity (SNA) to the heart than to the kidney. To assess this observation more rigorously, we simultaneously measured changes in cardiac and renal SNA elicited by TMI and by epicardial and intracoronary bradykinin (BK). Experiments were performed in 19 chloralose-anesthetized dogs with sinoaortic denervation and vagotomy.

Reflexes mediated by cardiac sympathetic afferents during myocardial ischaemia: role of adenosine.

1. Myocardial ischaemia and infarction activate vagal and sympathetic sensory endings in the ischaemic myocardium, resulting in powerful reflex effects. The vagal afferents are either mechano- or chemosensitive, whereas sympathetic afferents may be mechano-, chemosensitive or both.

Photoacoustic Fibrinolysis: Pulsed-Wave, Mid-Infrared Laser-Clot Interaction.

Objectives: The purpose of this study was to determine whether a mid-infrared laser can induce selective fibrinolysis and to analyze the effect of altered fibrin structure (thin vs. thick fibers) on laser-clot interaction. Background: Mechanical disruption of thrombus can be achieved with balloon angioplasty, sonication, and thermal energy.

Evidence against reinnervation of cardiac vagal afferents after human orthotopic cardiac transplantation.

Background: Orthotopic cardiac transplantation results in total cardiac denervation. Recent studies in humans suggest that reinnervation of cardiac sympathetic nerves (cardiac efferents) may occur after cardiac transplantation. We hypothesized that reinnervation of cardiac afferents may occur as well.

Noninvasive detection of transplant coronary artery disease by dobutamine stress echocardiography.

Coronary artery disease has emerged as the leading cause of late morbidity and mortality in heart transplant recipients. The incidence of allograft coronary artery disease has been reported to be as high as 40% to 50% by 5 years. Coronary angiography remains the standard approach for surveillance of coronary artery disease in this patient population.

Vagal cardiopulmonary reflexes after left ventricular deafferentation.

Background: Cardiac transplantation and chronic myocardial infarction interrupt vagal afferent nerve fibers, which originate mainly from the ventricles. Marked abnormalities of reflexes mediated by cardiopulmonary receptors with vagal afferent fibers have been demonstrated after both cardiac transplantation and chronic myocardial infarction. The relation between these reflex abnormalities and ventricular deafferentation is not known.

Renal sympathetic responses to conflicting baroreceptor inputs: rapid ventricular pacing in dogs.

1. Ventricular tachycardia generates complex changes in baroreceptor input to the central nervous system: arterial baroreceptors are unloaded while cardiopulmonary receptors are stimulated. In humans with heart diseases, muscle sympathetic nerve activity increases during ventricular tachycardia.