Fragile Lives Page 28
bridge to recovery: the process whereby a ventricular assist device is used to sustain the circulation and rest an acutely failing heart pending recovery from a reversible condition. If the heart does not recover, a limited-duration pump can be replaced by a long-term implanted device.
bridge to transplant: the process whereby a ventricular assist device is used to prevent death from heart failure until a donor heart can be found. At the time of transplant the pump and diseased heart are both removed.
cannula: a plastic tube inserted into the heart or a blood vessel to carry blood or fluid.
cardiac catheterisation: a long fine-bore catheter is passed from the groin or wrist up into the heart or coronary arteries. Contrast medium is injected rapidly to demonstrate the internal anatomy of the heart or blood vessels. The catheter is also used to measure pressure within the chambers.
cardiac tamponade: a condition that occurs when blood or fluid accumulates within the pericardial sac under pressure, preventing the heart from filling.
cardiomyopathy: heart muscle disease. There are several causes, which may be impossible to define, thus the term ‘idiopathic’, meaning a disease of unknown cause. Can occur spontaneously in all age groups, after pregnancy or due to poisoning with alcohol or other toxic substances. Causes chronic heart failure.
cardioplegia: a cold (4°C) clear or blood-based solution infused into the coronary arteries to stop and protect the heart in a flaccid state during surgery with the heart–lung machine. Usually contains a high concentration of potassium. At the end of the repair the heart is reanimated by restoring normal coronary blood flow.
cardiopulmonary bypass (CPB): process whereby the patient’s blood is diverted away from the heart and lungs for the duration of the surgical repair. Contact of the patient’s blood with the synthetic surfaces in the pump-oxygenator system elicits an inflammatory response. This limits the safe duration of blood–foreign surface interaction. The longer the procedure, the more damaging is the whole-body inflammatory response.
capillaries: billions of microscopic single-cell-thick blood channels that exchange nutrients, oxygen, carbon dioxide and metabolic by-products with the tissues of the body.
CentriMag ventricular assist device: an external magnetically levitated centrifugal blood pump widely used for temporary circulatory support. Now marketed by Thoratec for use in cardiogenic shock.
chronic heart failure: the left ventricle fails gradually but inexorably due to a number of conditions, the commonest being coronary artery disease. Causes severe breathlessness and fatigue. Conveys a high mortality rate by two years.
congenital heart disease: heart deformity that the patient is born with (e.g. atrial septal defect, ventricular septal defect, dextrocardia).
coronary artery bypass grafts: operation to bypass the narrowing of the heart’s own arteries using pieces of the patient’s chest-wall arteries, forearm arteries or leg veins.
coronary artery disease: gradual narrowing of the coronary arteries by atheroma. These fatty, cholesterol-based plaques are prone to rupture when they suddenly occlude the vessel, which then clots (coronary thrombosis).
CT scan: X-ray-based three-dimensional imaging of the chest and heart. By adding contrast medium the coronary arteries can be shown in detail.
deoxygenated blood: bluish blood leaving the tissues and returning to the right heart, now low in oxygen and carrying carbon dioxide to be expelled by the lungs. See also oxygenated blood.
diastole: relaxation and filling phase of the ventricles.
echocardiogram: non-invasive ultrasound examination of the heart chambers.
electrocautery: the electrical instrument used to cut through tissues and simultaneously coagulate blood vessels to stop bleeding.
endocarditis: bacterial infection that can destroy the heart valves.
extracorporeal membrane oxygenation (ECMO): circuit outside the body with blood pump and long-term oxygenator (lasting days) used for temporary circulatory support in acute heart failure or severe lung failure. Attached to the body by percutaneous (through the skin) cannulation of the blood vessels to the leg. Usually functions as a bridge to a longer-term pump or transplantation.
heart–lung machine: circuit outside the body to keep the patient alive while the heart is stopped for repair. Contains a mechanical blood pump and a short-term (lasting hours) complex gas exchange mechanism known as the oxygenator (artificial lung). Other pumps are used for suction of blood into the reservoir and for delivery of cardioplegia fluid to stop the heart.
HeartMate left ventricular assist device: an obsolete large pulsatile implantable pump widely used for bridge to transplant in the 1990s. The first device to be implanted on a permanent basis. Thoratec went on to produce a successful rotary blood pump for permanent use.
heart transplant: removal of the patient’s diseased and failing heart, then replacement with an organ from a brain-dead donor.
heart valve replacement: removal of a diseased heart valve, then replacement with a prosthetic valve. Prosthetic valves can be biological (e.g. pig’s valve) or mechanical (e.g. pyrolytic carbon tilting disc valves).
hypertension: high blood pressure that makes the heart work too hard. The level depends upon tone in the peripheral arteries. Can be very high (>200/120) and cause heart failure or stroke.
hypotension: low blood pressure (<90/60). Can be caused by blood loss or left ventricular failure. When pressure falls below 60/40 the patient is in shock and needs urgent resuscitation, and the kidneys cease to produce urine.
intra-aortic balloon pump (IABP): long, sausage-shaped balloon that’s inserted into the aorta. When inflated in diastole and deflated during systole it serves to lower the resistance against which the left ventricle has to pump. Used to support the left ventricle when it’s struggling to cope. Ineffective in shock states when the blood pressure or blood volume is low.
Jarvik 2000: thumb-sized rotary blood pump that is inserted into the failing heart on a long-term basis. A long-term ‘off the shelf’ solution for severe heart failure. The longest implant exceeds eight years.
left atrium: collecting chamber for blood returning to the heart from the lungs. The blood then passes through the mitral valve into the left ventricle. See also right atrium.
left ventricle: powerful, thick-walled conical chamber that pumps blood through the aortic valve and around the body. See also right ventricle.
left ventricular assist device (LVAD): mechanical blood pump to maintain the circulation and rest the ventricles when the heart fails catastrophically. The cannulas are inserted into the chambers of the heart. There are inexpensive temporary external devices suitable for several weeks of support in acute heart failure (e.g. CentriMag or Berlin Heart). The small, implantable but very expensive high-speed rotary blood pumps (e.g. Jarvik 2000) can be used for as long as ten years in chronic heart failure. As such, the long-term LVADs offer an off-the-shelf alternative to heart transplantation.
magnetic resonance imaging (MRI): non-invasive (without X-ray), detailed study of an organ’s (e.g. heart) morphology.
metabolic derangement: consequence of poor tissue blood flow. Arteries to the muscles clamp down and the tissues produce lactic acid and other toxic metabolites.
mitral stenosis: narrowing of the mitral valve between left atrium and left ventricle caused by rheumatic fever. Flow through the valve is restricted, causing breathlessness and chronic fatigue.
myocardial infarction: death of part of the heart when a coronary artery occludes suddenly. Dead muscle is replaced by scar.
myocarditis: virus infection of the heart muscle itself, causing the heart to fail.
oxygenated blood: bright red blood saturated with oxygen and pumped around the body by the left ventricle. See also deoxygenated blood.
perfusionist: technician who controls the heart–lung machine and ventricular assist devices.
pericardium: fibrous sac that surrounds the heart. Can be used as patch material in the heart
. Calf pericardium is used to make bioprosthetic heart valves.
pulmonary artery: large, thin-walled vessel that carries blood from the right ventricle to the lungs. It bifurcates into right and left pulmonary arteries.
pulmonary oedema: ‘water on the lungs’ that occurs when the left ventricle fails. Is often frothy and blood-stained.
pulmonary veins: four veins leaving the lungs to bring blood back to the heart.
reperfusion: the process whereby blood is allowed back into the coronary arteries and heart muscle following cardioplegia and cardiac arrest during surgery. The heart is reanimated and begins to beat again.
rheumatic fever: autoimmune condition triggered by a streptococcus bacterial infection that damages the heart valves and joints. Very common cause of valve disease in the pre-antibiotic era.
right atrium: collecting chamber for blood returning to the heart from the body via the veins. The blood then passes through the tricuspid valve into the right ventricle. See also left atrium.
right ventricle: crescent-shaped pumping chamber that propels blood through the pulmonary valve and to the lungs. See also left ventricle.
shock: condition when the heart cannot continue to supply sufficient blood and oxygen to the tissues. Cardiogenic shock occurs after a heart attack. Haemorrhagic shock follows profuse bleeding of two litres or more.
systole: phase of the heart cycle when the ventricles contract to expel blood.
veins: thinner-walled vessels that return blood to the heart.
vena cava: large vein entering the right atrium. The superior vena cava drains the upper part of the body; the inferior vena cava drains the lower half.
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