Q.What is known as Sick Sinus Syndrome?

The chapter's disorders largely trace back to one underlying process: the narrowing or blockage of blood vessels. Hypertension - persistently high blood pressure (diastolic above 90 mm Hg or systolic above 150 mm Hg, against a normal 120/80 mm Hg) - is the most common circulatory disease and, left uncontrolled, can damage the heart, brain and kidneys. Coronary heart disease develops when coronary arteries become lined with atheroma (a build-up of cholesterol, fibres, dead muscle and platelets); this atherosclerosis stiffens and narrows the artery and can trigger a coronary thrombus, which causes a heart attack. Stroke occurs when a vessel supplying the brain bursts (haemorrhage) or is blocked by atherosclerosis or thrombus, killing the brain tissue it served (cerebral infarction). Angina pectoris is the ischaemic chest pain of early coronary heart disease, caused when an atheroma partially blocks a coronary artery. Myocardial infarction (heart attack) is severe, usually thrombus-caused, loss of blood supply to the heart muscle, killing muscle fibres and - if angina from it persists - progressing to heart failure, during which the Frank-Starling curve shifts down and to the right so the heart ejects a smaller stroke volume for a given filling. Rheumatic heart disease …