myocardial ischemia Flashcards
myocardial ischemia
Imbalance between myocardial oxygen supply and myocardial oxygen demand
Coronary artery occlusion greater than 70% produces myocardial ischemia
triggers include exercise and mental stress
What effects myocardial oxygen supply?
arterioVenous oxygen difference
Coronary blood flow (aortic pressure and coronary vascular resistance)
what affects myocardial oxygen demand?
heart rate
Contractility
Wall tension (ventricular volume and pressure)
Ischemia presents with
ECG changes
Angina
Left ventricular dysfunction
stable angina or angina pectoris
Discomfort and pain, pressure heaviness tightness
last for several minutes
Substernal, precordial, shoulder, arm, throat, jaw
Relieved by rest or nitroglycerin
unstable angina
change in stable angina pattern
Accelerating in frequency
lasting longer
Less responsive to medication
Pain occurring at rest
Due to plaque rupture, ulceration, thrombus formation
prinzmetal variant angina
vasospasms
chest pain due to artery being in vasospasm
associated with the ST segment elevation
May occur at rest and not seen with exertion or stress
Not associated with increased myocardial VO2 demand
Relieved with nitroglycerin
Asymptomatic, silent myocardial ischemia
do not complain of chest pain
Peripheral neuropathy
Elderly patients and peripheral neuropathy patients may present with angina equivalence
dyspnea fatigue, lightheadedness, belching with exercise, or stress
myocardial infarction
Prolonged myocardial ischemia
Complete interruption of blood supply
Clinical presentation of MI
set an onset of chest pain or discomfort
More than 30 minutes, unrelieved rest, and unrelieved after three doses of nitroglycerin
Pallor and shortness of breath
catacholamines cause sympathetic stimulation
Diaphoresis
Cool clammy skin
Reflex simulation of vomiting centers
Zone of infarction cell death/necrosis
18 to 24 hours after MI inflammatory response
2 to 4 days necrosis
4- 10 days debris cleared collagen, matrix
10-14 days weak fibrotic scar tissue
6-8 completion of an elastic scar tissue
Transmural myocardial infarction
Full thickness
ST elevation
Q wave changes
subendocardial MI
partial thickness
ST wave changes
No significant q wave changes
Right coronary artery affected
inferior location
ECG changes in 2,3 and aVF
Risk of atrioventricular block or arrhythmias
50% have right ventricular infarct
Left main affected infarct
Anterior and lateral location
V1-V6 I, aVL
Pump dysfunction or failure
