Which is the MAIN risk factor for diastolic dysfunction?
1. Diabetic heart disease
2. Hypertrophic cardiomyopathy
3. Hypertension
4. Coronary heart disease - ANSWER3. Hypertension
Major risk factors include:
- HTN (major)
- HOCM
- CAD
- diabetic heart disease
- restrictive cardiomyopathy.
Which of the following statements regarding diastolic failure is TRUE?
1. Pulmonary oedema is an uncommon presentation
2. Diabetes mellitus is the most common predisposing condition
3. It is more common in men
4. Cardiac output is preserved at rest - ANSWER4. Cardiac output is preserved at rest
Diastolic FAILURE occurs mostly in patients >65yoa. More commonly in WOMEN.
<b>Causes:</b>
- HTN (commonest)
, - DM
- obesity
- bilateral renal artery stenosis
- idiopathic
The decrease in the ability of the LV to relax and fill may stem from myocardial fibrosis (IHD,
cardiomyopathies), infiltrative diseases (amyloidosis), and restrictive pericarditis.
With diastolic failure, CO is RELATIVELY PRESERVED at REST. However, the heart is unable to increase
its output in response to an increase in metabolic demands (e.g., exercise). As the LV is unable to
expand, any increase in filling pressure is immediately referred back into the pulmonary system
causing (flash) APO.
Which of the following is a consequence of a myocardial infarction?
1. There is loss of contractility within 60 seconds
2. ATP reduction of 50% occurs within 20min
3. Irreversible cell injury occurs after 60min
4. Microvascular injury occurs after 2hrs - ANSWER1. There is loss of contractility within 60 seconds
Only severe ischaemia, lasting >20-40min, leads to irreversible cell damage (necrosis).
The extent of necrosis is largely complete within 3-6hrs in experimental models. Progression of
necrosis in humans follows a more protracted course of 6-12hrs. In these patients coronary arterial
collateral system, often stimulated by chronic ischaemia, is better developed and thereby more
effective.
Approximate times of onset of key events in ischaemia:
- onset of ATP depletion occurs in SECONDS
- ATP reduced to 50% of normal in 10min and 10% of normal in 40min
- LOSS of CONTRACTILITY occurs in <2min
- IRREVERSIBLE cell INJURY occurs in 20-40min
- MICROVASCULAR injury occurs >1hr
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