L8 - Ischemic Heart Disease Flashcards
IHD may become clinically manifest as
- chest discomfort
* 2. heart failure
* 3. abnormal EKG or stress test
* 4. arrhythmias, sometimes with resulting syncope or “sudden cardiac death”
- chest discomfort
What is the most common cause of death in the US?
Sudden cardiac death (due to arrhythmias)
Which is false?
A. >60% are “sudden” (Occur Within Minutes to Hours of Onset of Symptoms or Without Warning), of which 1/3 are instantaneous & >70% occur outside hospital
B. Most sudden cardiac deaths (SCD’s) are due to ventricular fibrillation
C. Most SCD’s are associated with underlying coronary atherosclerosis and in many, old remote myocardial infarction (M.I.).
D. In the majority of sudden cardiac death an acute M.I. is responsible for triggering the arrhythmia causing the SCD episode
D. is NOT responsible for triggering arrhythmia
IHD is an imbalance where myocardial ____ exceed myocardial _________
- oxygen demand
2. blood flow
4 major determinants of myocardial o2 demand
a. Intraventricular systolic pressure
b. Ventricular cavity radius (cavity radius times systolic pressure equals ventricular wall tension by the Laplace equation).
c. Heart rate
d. Contractility of the muscle
3 sudden cardiac death mechanisms and which ones are reversible?
- ventricular tachycardia - 10%
- ventricular fibrillation - 60%
- asystole EMD and bradycardia- 30%
First 2 are reversible
Angina pectoris is a consequence of myocardial ______ exceeding myocardial ________
- oxygen demand
2. oxygen supply
- coronary blood flow
- oxygen delivery (hematocrit, o2 saturation)
CBF (AV)O2
o2 supply
- blood pressure (afterload)
- Ventricular volume (preload)
- Heart rate
- contractility
MVO2
o2 demand
Formula that is related to the regulation of coronary blood flow to meet increased myocardial o2 demand
F = P/F F = coronary blood flow P = perfusion pressure gradient R = coronary resistance
How can you increase perfusion pressure gradient to increase coronary blood flow? (2)
- increased aortic diastolic pressure
2. decreased LV diastolic pressure
How can you decrease coronary resistance to increase coronary blood flow?
- Autoregulation (metabolic factors)
- Neural factors
- Pharmacologic agents
Etiology of ischemic heart disease
- • Aortic Outflow Tract Disease With Pathological Left Ventricular Hypertrophy e.g. Aortic Valve Stenosis or Insuffiency or Idiopathic Hypertrophic Cardiomyopathy
- • Primarily a Matter of Increased MVO2. Also Inadequate Capillary Proliferation To Keep Up with the Hypertrophy
- Vast Majority Due To:
• Disease of Coronary Arteries
• Atherosclerosis
- Described as: Tightness, Ache, Squeezing, Pressure, Weight or Burning
- Often Described with Palm or Clenched Fist Pressed Against the Sternum – Levine’s Sign
- Most Commonly Substernal
- May Radiate To or Be Only Felt in Shoulders &/or Arms, Neck, Mandible, or Interscapular Areas
STABLE Angina
What precipitates stable angina?
Events that increase MVO2 (o2 demand)
- cold environment
- heavy meal
- early in day
- superimposed isometrics
What is the duration of stable angina?
- *NEVER a Few Seconds
- *Occasionally One Minute, Usually 3 To 5 Minutes, Rarely 15 to 20 Minutes.
- *Prompt Relief After Discontinuation of Precipitating Cause &/or Use of s.l. NTG.
- Subinguinal nitroglycerine
- *Longer Duration Indicates Unstable Angina
Classification of chest pain:
- typical angina (definite)
- atypical angina (probable)
- Noncardiac chest pain
Typical:
(1) Substernal Chest Discomfort with a characteristic quality & duration that is
(2) Provoked by exertion or emotional stress and
(3) Relieved by rest or nitroglycerin.
When do you do a graded treadmill test?
For stable typical or probably angina at time of:
- inita evaluation
- changing ischemic symptoms
NOT if presenting with acute coronary syndromes (acute MI, unstable angina)
Advantage of treadmill test
Correlates patient activity and myocardial o2 demands with:
- objective evidence of ischemia and
- specific cardiac symptoms
What is the classic presentation of stable angina on the EKG of the treadmill test?
ST segments start to sag down
How else can you confirm diagnosis of angina aside from the treadmill test?
- Cardiac perfusion imaging studies
2. stress echo
T/F Angina is a pathophysiologic or functional diagnosis
T
What is the most definitive test of presence or absence of abnormality of the epicardial coronary arteries?
Coronary angiography
What percentage of narrowing of the coronary artery is required to limit max coronary flow?
50%
