The heart
Laurie K. McCorry, Martin M. Zdanowicz, Cynthia Y. Gonnella in Essentials of Human Physiology and Pathophysiology for Pharmacy and Allied Health, 2019
The coronary arteries supply oxygenated blood to the myocardium. The coronary arteries fill with oxygenated blood from the aorta during diastole. At rest, the delivery of oxygenated blood and nutrients supplied by the coronary arteries should match the metabolic demands of the heart. Myocardial oxygen demand is increased by factors such as exercise or increased preload and afterload, which increase heart rate and contractility. When the metabolic needs of the heart increase, coronary blood flow should increase accordingly. Coronary blood flow is regulated locally through the accumulation of cardiac metabolites such as lactic acid, CO2 and adenosine, which cause coronary artery vasodilation and increased blood flow. Increased cardiac workload also results in increased shear forces in the coronary arteries that distends them and triggers the release of nitric oxide from the endothelium that dilates the vascular smooth muscle and increases coronary blood flow.
SBA Answers and Explanations
Vivian A. Elwell, Jonathan M. Fishman, Rajat Chowdhury in SBAs for the MRCS Part A, 2018
The heart is composed of cardiac muscle. This cardiac muscle receives the oxygen and nutrients that it requires to pump effectively through the coronary arteries. There are two principal coronary arteries: the right and the left. The right coronary originates from the anterior aortic sinus, whereas the left coronary artery originates from the left posterior aortic sinus. The left coronary artery divides into an anterior interventricular (or left anterior descending) artery and circumflex branches. The right coronary gives off the posterior interventricular (posterior descending) artery. The right coronary supplies the right atrium and part of the left atrium, the SA node in 60 per cent of cases, the right ventricle, the posterior part of the interventricular septum, and the AV node in 80 per cent of cases. The left coronary artery supplies the left atrium, left ventricle, anterior interventricular septum, SA node in 40 per cent of cases, and AV node in 20 per cent of cases.
The cardiovascular system
C. Simon Herrington in Muir's Textbook of Pathology, 2020
An understanding of how coronary artery atherosclerosis produces clinical disease must be based on knowledge of the anatomy, histological structure, and physiology of the coronary arteries themselves. There are two major coronary arteries, left and right, which form separate arterial systems, unless there is gradual narrowing, when collateral vessels develop between them. The epicardial surface coronary arteries have a well-developed medial coat containing very few elastic and numerous smooth muscle cells. Medial tone can therefore vary and significantly alter lumen calibre. The blood flow to the myocardium is unique in that it does not occur in systole when the left ventricle is contracting. The epicardial arteries fill in systole but flow into the myocardium occurs in diastole. As the ventricular myocardium relaxes, blood is sucked in from the epicardial arteries and aortic root above the closed aortic valve.
Pathobiology and evolving therapies of coronary artery vasospasm
Published in Baylor University Medical Center Proceedings, 2021
Monish A. Sheth, Robert J. Widmer, Hari K. Dandapantula
Nitroglycerin is an endothelium-independent vasoactive agent with the capacity to diminish myocardial oxygen demand by dilating peripheral arteries and veins, thereby causing a resultant fall in left ventricular preload and afterload. It also augments myocardial oxygen supply by dilating epicardial coronary arteries and increasing collateral and subendocardial blood flow.40 Long-acting nitrates are very useful in patients with circadian-pattern anginal attacks when taken at night. Shorter-acting nitrate therapy is useful for acute CAV. Headache and hypotension are the most common side effects limiting therapy with nitrates. Prospective double-blind studies with CCB compared with nitrates have reported similar efficacy for both agents in reducing spasm occurrence.41 Some have argued for use of both agents concurrently. CCB and nitrate therapy needs to be balanced with guideline-directed medical therapy in patients with CAD and congestive heart failure.
De Winter electrocardiographic pattern in a young patient with acute myocardial infarction
Published in Baylor University Medical Center Proceedings, 2023
The patient was taken for immediate coronary angiogram through the right radial route. Loading doses of aspirin, ticagrelor, and atorvastatin were administered. Coronary angiogram (Figure 2a and b) showed 95% stenosis of the proximal LAD with thrombus. The left main, left circumflex, and right coronary arteries were normal. The proximal LAD lesion was dilated and stented using a 3.5 × 28 mm everolimus-eluting stent (Figure 2c). Percutaneous transluminal coronary angioplasty was done through the right femoral route, as he had a severe radial artery spasm following coronary angiogram. An ECG 1 hour after the procedure showed complete disappearance of the de Winter pattern (Figure 1b). After about 36 hours, the ECG showed T wave inversion in leads I, aVL, and V1–V6 (Figure 1c). An echocardiogram the next day showed mild hypokinesia and good left ventricular systolic function. The patient was discharged home after 3 days. Investigations for premature coronary artery disease, including serum homocysteine, lipid profile, and lipoprotein(a), were negative.
Giant tumour-like pericarditis on CT and echocardiography
Published in Acta Cardiologica, 2021
Yang Wang, Huabao Li, Jianjun Ge
A 60-year-old Chinese woman complaining of progressive dyspnoea, asthenia and bilateral lower extremity oedema was admitted to our hospital. Transthoracic echocardiography showed a large solid mass compressing the right ventricle. Chest computed tomography (CT) with contrast showed a solid mass (12 × 47.7 cm) attached to the thickened, calcified pericardium (Figure 1). The solid mass had a heterogeneous density and was clearly demarcated from the cardiac cavity. Coronary angiography showed normal left and right coronary arteries. The patient had a history of hypertension but denied a history of tuberculosis, surgery or other diseases and had no recurrent low fever or night sweats. The laboratory findings indicated that the brain natriuretic peptide (1349 pg/ml) and C reactive protein (12.40 mg/L) levels and the erythrocyte sedimentation rate (25.0 mm/h) were elevated. A purified protein derivative (PPD) skin test and HIV test were negative. No acid-fast bacilli were found in a microbiological examination of the sputum. Surgical intervention was successfully performed to resect the mass to relieve the pressure on the heart. A large amount of caseous necrosis was observed between the parietal pericardium and the visceral layer during the operation (Figure 2). Histopathological findings showed hyaline degeneration and calcification, local fibrinous necrosis with haemorrhage, organisation, and focal inflammatory cell infiltration (Figure 3). Acid-fast bacilli smear and culture in the pericardial mass were negative.