Week 2: Cardiology Flashcards
Features of the Coronary Circulation
-High O2 Consumption
-High Resting O2 Extraction
-Limited Anaerobic Capacity
As such, Adjustments to the supply of oxygen to cardiac muscle is governed by coronary vasomotor tone, and thus myocardium is vulnerable to disruptions to the coronary blood flow
What does restricted o2 supply lead to (myocardium)
-increased rate of glycolysis
-Hence lactate is produced faster than it can be uptaken
-pH shifts towards acidosis
-Leads to consequences of ischema and potential pain typical of angina
Chronic Stable Angina vs Unstable Angina
-Stable = coronary flow impaired under conditions of high O2 demand leading to ischemia
-Unstable = Coronary flow impaired under resting conditions leading to ischemia
Characteristics of Angina
Grades of Angina
Dermatone
Specific areas of the skin that are supplied by individual spinal nerves
Dermatone C3-C4 and C5-T1
C3-C4:The neck and upper shoulders
C5-T1: upper chest, shoulders and upper back
Causes of Acute Coronary Syndrome
-Atherosclerosis (which results in embolus blocking coronary artery) (MOST COMMON)
-Coronary artery spasm
-Spontaneous Coronary Artery Dissection (SCAD
-Coronary microvascular dysfunction
-MI with non obstructed coronary arteries
How Does SCAD lead to ACS
Sudden tearing of layers in coronary artery wall, leading to a blockage
How does a coronary artery spasm lead to ACS
Temporary constriction of a coronary artery, restricting blood flow to the heart
How does Coronary microvascular dysfunction lead to ACS
Impaired function of the small vessels in the heard affecting blood supply to the heart muscle
Pathophysiology of infarction due to atherosclerosis
- Plaque formation
- Plaque erosion/rupture
- Occluded coronary artery
- Arterial pressure drop across stenosis
- Reduced blood floe
- Poor oxygen perfusion
- Oxygen supply and demand mismatch
- Infarction
Symptoms of MI
-Tight Chest pain in substernal area with radiation to the left arm or jaw (2/3 of cases)
-Dyspnea
-Nausea
-Palpitations
-Weakness
-Diaphoresis (excessive sweating)
NB: atypical presentation can be present in women, diabetics, elderly
STEMI
ST-Elevated myocardial infarction
-Serve heart attack with ST segment elevation on the ECG
-Indicates a transmural Infarction/full vessel obstruction of coronary artery
-Elevated Troponins
-type of ACS
NSTEMI
Non-ST-elevated myocardial infarction
- Partial heart attack with no ST-segment elevation
- Indicating partial coronary artery blockage / subendocardial infarction
- Type of ACS
- Elevated Troponin levels, ECG looks similar to unstable angina
Unstable angina
-Chest pain or discomfort caused by reduced blood flow to the heart, often a precursor to a heart attack (MI).
-only partial blockage of artery
-normal Troponins
-ECG looks similar to to NSTEMI
Differentiating between Stable Angina, Unstable Angina, STEMIA and NSTEMI
Patient History is used to differentiate stable angina (relieved by rest)
Troponin Levels differentiates Unstable angina (not elevated) from NSTEMI and STEMI (elevated)
ECG differentiates STEMI (ST elevation) from NSTEMI and Unstable Angina (normal, inverted t waves, or st depression) and Stable Angina (Normal)
Angiography
Imaging modality that enables visitation of blood vessels, can allow occlusions to be observed
PCI
Percutaneous Coronary Intervention AKA angioplasty
a catheter with a deflated balloon at its tip is inserted into the narrowed artery, and the balloon is inflated to compress the plaque and widen the vessel. A stent is often placed to keep the artery open, reducing the risk of re-narrowing.
Helps restore blood flow to heart muscle
Lateral surface of the heart ECG leads
I, aVL, V5, V6
Supplied by the Left circumflex artery
Inferior surface of the heart ECG leads
II, III, aVF
Supplied by the Right marginal atery
Anterior surface of the heart ECG leads
V3, V4
Supplied by the Left anterior descending artery (and RCA)
NB: the LAD is also known as as the widow maker due to high morbidity associated with an LAD infarction
Septal Surface of the Heart ECG leads
V1, V2
Supplied by the Left anterior desceding artery
ECG findings and Serum Troponin in Unstable Angina
ECG: ST-segment depression; T wave inversion
Serum troponin: Normal
ECG findings and Serum Troponin in NSTEMI
ECG: ST-Segment depression; T wave inversion
Serum Troponin: Rise and fall
ECG findings and Serum Troponin in STEMI
ECG: ST segment elevation
Serum Troponin: rise and fall
NSTEMI ECG
STEMI ECG
Normal ECG
Coronary Angiography - Why and How
Why: helps evaluate the patency and condition of the coronary arteries.
How: involves threading a catheter through a blood vessel (typically the femoral or radial artery) and advancing it to the coronary arteries under X-ray guidance. A contrast dye is injected through the catheter directly into the coronary arteries. This dye makes the blood vessels visible on X-ray images, allowing the cardiologist to assess blood flow and detect any stenosis.
Reperfusion in ACS management
Thrombolytics (if <30mins) or PCI/angioplasty (<90mins)
Restores blood flow
Pharmacological Managment of ACS
MONA
-Morphine
-oxygen
-nitrates (GTN)
-aspirin/anti-platelet
+ treat if hypotension or tachycardic
Secondary ACS management
-Dual Anti-platelet therapy (used for 12 months post MI)
-Statins (balance cholesterol, reducing formation of plaque)
-ACE inhibitors (reduces blood pressure)
-Beta Blockers (have a negative iontropic effect reducing heart workload and lower BP)
-lifestyle changes (smoking, alcohol, diet)
-Cardiologist referral for monitoring
Label
R’ wave
(Second positive deflection (aka second sharp up))