Coronary Artery Disease (CAD) Flashcards
What does it mean to be Right Dominant?
PDA supplied by RCA (85% of population)
What does it mean to be Left Dominant?
PDA supplied by LCx (15% of population)
What are the effects of a Left main occlusion in a Left dominant heart?
Loss of anterior, lateral, and posterior walls
The more ____ the occlusion, the more damage occurs.
Proximal (closer to the aorta)
Describe the Right Coronary Artery?
-Originates at the right aortic sinus
-Supplies 25-35% of LV
-Supplies SA node (60% of ppl)
RCA Occlusion causes what symptoms?
Bradycardia or arrhythmias
What are the two branches of the RCA?
-PDA (85% of people)
-Right Ventricular
What is the PDA?
-Supplies inferior wall, septum and posteromedial papillary muscle
-Gives rise to septals
What is the Right Ventricular branch of the RCA?
-Supplies anterior RV, SA Node
-Has Acute Marginal Branches
Describe the Left Coronary Artery.
“widow-maker”
-Originates as Left Main (0-10mm length)
-Left Main splits into LAD and Left Circumflex
Describe the LAD.
-Travels down interventricular groove to apex
-Gives off Septals and Diagonals
-37% of people have ramus (looks like a 1st diag)
-Supplies 45-55% of LV
-Supplies septum, bundle branches, and Purkinje system
Describe the Left Circumflex.
-In 15% of people, PDA is off L Cfx
-Travels down left AV groove
-Gives off Obtuse Marginal (OM) Branches
-Supplies Posterolateral- LV, Lateral Wall of LV, SA node- 38%, and 15-25% of LV (unless left dominant- then 50%).
What EKG changes are seen with Left Main occlusion?
V1-V6
-Affects entire LV
What EKG changes are seen with LAD Occlusion?
V1-V4
-Affects Anterior LV
What EKG changes are seen with Left Circumflex Occlusion?
I, aVL, V5, V6
-Affects Lateral LV
What EKG changes are seen with RCA Occlusion?
II, III, aVF
-Affects RV & posterior LV
How do you calculate Coronary Perfusion Pressure (CPP)?
CPP = AoDP – LVEDP
-normal 60-80, autoregulated between 50-150mmhg
-Coronary blood flow mainly occurs during diastole
-Increased HR decreases time for diastolic filling
What are the 3 ways to optimize CPP?
1) Can increase DBP
2) Can lower LVEDP
3) Lower HR (Heart at rest should have a low LVEDP, increases width of CPP gradient).
How does coronary sinus SvO2 compare to systemic SvO2?
Systemic SVO2 = 70% vs. coronary sinus SVO2 = 35-50%
-Cardiac muscle extensively extracts O2.
-Ischemia develops when O2 demand > supply.
How do you calculate Coronary Blood Flow (CBF)?
Coronary Blood Flow (CBF) = Coronary Perfusion Pressure (CPP) / Coronary Vascular Resistance (CVR)
-Normal value = 225 – 250 mL / min
-Autoregulated between 50-150 mmHg
What factors INCREASE Coronary Vascular Resistance (CVR)?
-Inc O2, Dec CO2, Dec H+
-Inc Alpha-Adrenergic tone (constriction of epicardial arteries)
-Inc Cholinergic tone
-Inc Vasopressin (ADH), Angiotensin, and Thromboxane
What factors DECREASE Coronary Vascular Resistance (CVR)?
-Dec O2, Inc CO2, Inc H+ (Decreased O2 causes the release of vasodilator substances)
-Inc Beta-Adrenergic tone
-Inc Prostacyclin
-Inc Nitric Oxide, Inc Endothelium-derived factor, Inc Prostaglandin (I2)
What is a Left Main Equivalency?
If you have 2 proximal and a distal in the LAD, that is a “L Main Equivalent”.
-50% in one area + 50% in another is the same as Left Main.
-Sequential lesions are additive.
Why do older patients with CAD tend to do better than younger?
Older patients develop collaterals over time
What are the 3 main determinants of Myocardial O2 Consumption (Demand)?
-HR
-Contractility
-Wall Stress
How does HR affect Myocardial O2 Consumption?
The most important factor.
-Doubling of HR more than doubles the O2 demand.
How does Contractility affect Myocardial O2 Consumption?
-More contraction = more energy required = more O2 required
-Approximated by the ESPVR curve on PV Loop
-Echocardiogram gives most accurate determination
How does Wall Stress affect Myocardial O2 Consumption?
-Law of LaPlace: Tension (wall stress) = (Pressure x radius) / (2 x wall thickness)
-Doubling MAP more than doubles MVO2 (Decreases SVR to decrease O2 demand)
-Inc PL increases demand
-Inc wall thickness decreases wall tension (Hypertrophy results in response to increased AL)
MI in the Posterior Wall of the heart will cause what ECG Changes?
Tall R Waves, ST segment depression, and upright T waves in V1-V4 (reciprocal changes)
Which is the preferred Induction Agent for Cardiac Tamponade?
Ketamine
