TUTORIAL: Valvular disease and heart failure Flashcards
How do you calculate cardiac output?
Cardiac output= heart rate x stroke volume
Cardiac output is the volume of blood the heart pumps in one minute. Frequently given in Litres/minute (but can be also cm3/min)
How do you calculate stroke volume?
Stroke volume= end diastolic vol- end systolic vol
How do you calculate ejection fraction?
EF (%)= (stroke vol / end diastolic volume) x 100
Ejection fraction is the volumetric fraction of blood ejected by the ventricle with each contraction. It is commonly given as a percentage (hence multiplication by 100)
How do you calculate mean arterial pressure?
At normal resting heart rates MAP can be estimated using:
1/3 SBP + 2/3 DBP
ALSO:
mean arterial pressure (MAP) = (Cardiac output (CO) x systemic vascular resistance (SVR)) + central venous pressure (CVP)
the mean arterial pressure is an average arterial blood pressure throughout a single cardiac cycle of systole and diastole. In health, a MAP >65 mmHg represents the pressure necessary to adequately perfuse the body organs. The estimation of MAP is useable at rest but during exertion (at high heart rate) MAP moves more closely toward an average of SP and DP
What is infective endocarditis?
Rare but potentially fatal infection of the inner lining of the heart (endocardium) or vascular enothelium of the heart
Typically affects the heart valves. It is usually the result of bacteria entering the blood stream and forming ”a vegetation” (a bacterial infection surrounded by a layer of platelets and fibrin) in the endocardium. Streptococci (20-40 % of cases) are the most common infection.
How would you diagnose infective endocarditis?
Fever, malaise, sweats and unexplained weight loss are common symptoms
There may be a new heart murmur on examination
Blood tests show anaemia and raised markers of infection
Blood cultures may isolate a microorganism
Echocardiogram can show a vegetation, abscess, valve perforation and/or new dehiscence of prosthetic valve. Often there is regurgitation of the affected valve
Transoesophageal echo has higher sensitivity compared with transthoracic
What features of heart decompensation would you look for in suspected infective endocarditis?
Symptoms include shortness of breath, frequent coughing, swelling of the legs and abdomen, fatigue
Clinical signs include raised JVP, lung crackles and oedema
Other complications:
Vascular and embolic phenomena
(stroke, Janeway lesions, splinter/ conjunctival haemorrhages)
Immunological phenomena
(Osler’s nodes, Roth spots)
Which part of the heart does infective endocarditis affect?
Infective endocarditis affects the endocardium, especially the valves of the heart (more common for bacteria to attach to the endocardium if underlying damage is present, and this occurs more frequently at sites of turbulent blood flow such as the valves of the heart.)
Aortic valve is affected most frequently (aortic > mitral > right-sided valves)
How might the part of the heart affected by infective endocarditis vary for intravenous drug users?
Intravenous drug users are at increased risk of infective endocarditis due to repeated injection – potentially exposing their bloodstream to bacteria on the surface of the skin or use of non-sterile needles.
also a complication of routine surgeries such as dental surgery. It is also more common in individuals that are immunosuppressed or have congenital heart defects leading to damaged endocardium.
What criteria is used to monitor infective endocarditis?
“Duke’s criteria”
Major criteria
Minor criteria
Definite endocarditis
Possible endocarditis
Rejected endocarditis
(look up to see specifics)
What is the definition of dilated cardiomyopathy?
dilated cardiomyopathy is characterised by dilated and thin-walled cardiac chambers with reduced contractility
Dilation of the chambers leads to reduced contractility. Echo shows a dilated left ventricle with reduced systolic function (ejection fraction) and typically global hypokinesis
What are the commonest causes of dilated cardiomyopathy?
Idiopathic, genetic, toxins (alcohol, cardiotoxic chemotherapy), pregnancy (peripartum cardiomyopathy), viral infections (myocarditis), tachycardia-related cardiomyopathy, thyroid disease, muscular dystrophies
How is dilated cardiomyopathy managed?
Medical heart failure therapy - ACE inhibitors, beta-blockers, mineralocorticoid receptor antagonists
Diuretics for fluid overload
Anticoagulation for atrial fibrillation
Cardiac devices – cardiac resynchronisation therapy and/or implantable cardioverter defibrillator
Transplant
What are some future implications following dilated cardiomyopathy diagnosis?
Risk of hospitalisation, cardiac arrhythmias, sudden cardiac death due to ventricular arrhythmia, and reduced survival
