This article is an effort to define the special properties of BB and its possible role in prevention of atrial fibrillation by permanent pacemakers.
The dynamic relationship between "spontaneous" fluctuations in arterial blood pressure (BP) and heart rate (HR) is increasingly being used to provide an estimate of resting cardiac baroreflex sensitivity. Given the ease of use and clinical utility, spontaneous methods are now also being used to examine cardiac baroreflex sensitivity in distinct subject groups during various laboratory stressors and tasks encountered during daily life, such as physical activity. However, the utility of such spontaneous measures to estimate cardiac baroreflex function during exercise remains unclear, particularly when comparing groups. Therefore, we tested the ability of spontaneous indices to detect age-related differences in cardiac baroreflex function during dynamic exercise. Beat-to-beat HR and BP were measured in eighteen young (24±1 yr) and sixteen older (59±1 yr) healthy middle-aged subjects at rest and during steady-state leg cycling. Estimates of spontaneous cardiac baroreflex sensitivity using the sequence technique (G SEQ ) and low frequency transfer function gain (G TF ) were compared to the operating point (G OP ) and maximal gain (G MAX ) of the full carotid-cardiac baroreflex function curve. At rest G SEQ , G TF , G OP and G MAX were all significantly lower in older subjects. During moderate intensity steady-state exercise no differences were observed in G SEQ and G TF (0.26±0.03 older vs. 0.32±0.04 younger bpm/mmHg; P>0.05), whereas G OP and G MAX (−0.21±0.02 older vs. −0.39±0.03 younger bpm/mmHg; P<0.05) remained lower in older subjects. These data indicate that spontaneous measures of cardiac baroreflex sensitivity alone provide limited information when comparing age-groups during exercise making actual differences in baroreflex function difficult to identify.
A subset of subjects undergoing myocardial perfusion imaging has perfusion abnormalities that are subsequently labeled false positive based on coronary angiography. We evaluated the long-term prevalence of cardiovascular events in these patients. We retrospectively identified 48 patients who had reversible perfusion abnormalities with myocardial perfusion imaging and normal coronary angiography. Patients with known coronary artery disease, left ventricular dysfunction, valvular disease, and cardiomyopathy were excluded. Patient follow-up, conducted for at least 3 (mean interval, 7.4) years from the index myocardial perfusion imaging, was accomplished by a review of medical records and telephone interviews. Study endpoints were cardiovascular events defined as sudden cardiac death, myocardial infarction, percutaneous coronary revascularization, coronary artery bypass grafting, and cerebrovascular or peripheral revascularization. Thirty-one percent (15 of 48) of the patients had cardiovascular events. Six of the 48 patients had coronary events. These patients had abnormal myocardial perfusion imaging and normal coronary angiogram. The time between myocardial perfusion imaging and coronary event was 0.5 to 8.67 years. There was a strong correlation between the regions of original perfusion abnormality and the ultimate coronary ischemia or revascularization. Abnormal findings on myocardial perfusion imaging may predict a higher prevalence of coronary and peripheral vascular events than suggested by a normal coronary angiogram.
Aortic dissection is a rare, potentially catastrophic vascular emergency. Early recognition of the clinical manifestations, rapid confirmation using imaging modalities, urgent administration of appropriate medication and expedient selection of definitive long-term therapy are key to preserving life and reducing morbidity. In recent years it has become increasingly clear that there is a relation between cocaine and aortic dissection. Cocaine serves as both a predisposing factor to aortic dissection due to its effect on aortic connective tissue and as a precipitating factor due to its propensity to produce abrupt and severe hypertension. While similarities exist in the clinical features and diagnostic methods between cocainerelated aortic dissection and aortic dissection unrelated to cocaine use, there are important differences in management between these two syndromes which are rooted in the pharmacology and physiology of cocaine. An understanding of these differences is key to effective early and long-term management of cocaine-related aortic dissection.
Background: Prompt diagnosis and management of aortic dissection are key to reduce patient morbidity and mortality; hence the need to a have a high index of suspicion for this condition. We believe it's important to report this case because it underscores the relationship between cocaine abuse and aortic dissection. In addition it strongly emphasizes basic principles in medicine: patients should not be profiled, and chronic complaints may need reassessment.
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