case 2 -Pharmacological Treatment of Stable Angina & Hypertension Flashcards
(27 cards)
what is the myocardium only perfused with?
myocardium is only perfused with oxygenated blood during diastole
what is ventricular wall tension determined by?
ventricular wall tension is determined by the pressure inside the chamber, the chamber volume (which affects the radius), and the thickness of the ventricular wall
what is myocardial oxygen demand proportional to?
myocardial oxygen demand is proportional to how hard the heart is having to work, i.e a function of the heart rate and ventricular wall tension
coronary blood flow is determined by what?
coronary blood flow is determined by myocardial oxygen demand
what does normal blood flow rely on?
Relies on vessels elastically expanding after pulsatile cardiac ejections
what can make the artery walls less elastic and more rigid?
Age and risk factors
what can happen as a result of the artery walls becoming less elastic and more rigid?
This increases cardiac inotropy (the ability of the myocardium to contract). This can then lead to ventricle hypertrophy and increased myocardial oxygen demand
what is the main feature of atherosclerosis?
growth of LDL cholesterol plaques in the sub-endothelium
what does atherosclerosis lead to?
leads to reduced oxygenation of tissues due to impaired blood flow
if the oxygenated blood supply can’t meet the myocardial demand, what is inevitable?
Ischaemia is inevitable
what is produced from myocardial anaerobic glycolysis?
Large quantities of (painful) lactate are generated from the pyruvate formed in myocardial anaerobic glycolysis
what’s angina?
Crushing, burning or tight chest pain, often accompanied with shortness of breath, nausea, sweating
(which coronary arteries and how narrowed they are determine the nature/severity of the symptoms, e.g chest pain)
stable angina is brough on by what?
stable angina is brough on by physical exertion (or emotional stress/exertion) and then as soon as the stressor is taken away, chest pain goes away within minutes
what are ECG changes that can indicate angina?
*ST-segment depression: A horizontal or down-sloping ST-segment depression that
lasts for more than 60–80 milliseconds after the QRS complex
*T-wave abnormalities: T-wave inversion, flattening, or elevation
*Pathological Q waves: Abnormal Q waves
*Left bundle branch block (LBBB): A blockage in the left bundle branch of the heart
*Arrhythmia: Usually ventricular extrasystoles
However, an ECG may be normal even if you have angina.
What other tests can help diagnose angina if an ECG is normal?
*Chest X-ray - Can help rule out other causes of chest pain, such as pneumonia and heart failure
*Blood tests - Can measure troponin levels in your blood to help differentiate between unstable angina and an MI
what is angiography?
Angiography is an X-ray imaging technique that can identify narrowing and occlusion of coronary arteries.
A radio-opaque contrast dye is injected into the coronaries via a catheter.
what is echocardiography?
echocardiography is a non-invasive ultrasound imaging technique that can identify chamber wall motion abnormalities that may indicate coronary artery disease
how can drugs be used in angina?
drugs can be used to reduce/relieve angina symptoms associated with an episode of exertional ischaemic stress, e.g drugs to vasodilate coronaries
and/or
drugs can be used prior to doing something strenuous/ be used to prevent/reduce incidences of angina episodes, e.g reducing the heart’s workload, and so limiting the amount of oxygen the heart needs to function/reducing the oxygen demand
how are organic nitrates used for stable angina?
organic nitrates used as symptomatic relief.
nitrates are drugs that (when absorbed into circulation) are modified to produce (NO), a potent vasodilator.
GTN (glyceryl-trinitrate) is broken down by the body into nitrates
relaxed vascular smooth muscle cells → vasodilation
how is GTN (glyceryl-trinitrate) broken dwon by the body into nitrates?
GTN→NO→sGC→cGMP
in vascular smooth muscle cells: MLC phosphatase ↑, Ca2+ ↓, K+ efflux ↑
how are beta blockers used for stable angina?
beta blockers used as prophylaxis.
Beta-1 adrenoreceptor antagonists are an effective means of reducing the onset of angina episodes/attacks.
beta blockers competitively inhibit beta-1 adrenoreceptors in cardiac tissue = a negative chronotropic and negative inotropic effect that reduces cardiac output (and hence myocardial oxygen demand).
example of beta blocker is bisoprolol
how are Ca2+ channel blockers used for stable angina?
Stops Ca2+ ion traffic through L-type voltage-gated channels in nodes (negative chronotrope) and in myocytes (as negative inotrope).
example of Ca2+ channel blocker is diltiazem
alternative 2 drugs that are also indicated for the treatment of stable angina are:
nicorandil
ivabradine
nicorandil mechanism of action
coronary vasodilator:
stimulates guanylyl cyclase to increase cGMP and thus reduces Ca2+ entry into vascular smooth muscle cells.
activates K+ATP channel effluxer, hyperpolarising cells thus preventing voltage-gated Ca2+ channel activity
