CV Function and ECGs Flashcards
Describe the relationship between resistance and radius of a blood vessel.
As radius increases by a certain amount, conductance (or blood flow) increases by the POWER of 4 of that radius change. Resistance increases to the inverse 4th power of that change. [R = 1/ r^4]
Ex:) Arterioles that decrease their diameter by 2x (vasoconstrict), will decrease their flow by 16x while their resistance is increases 16x that amount.
Describe the Equation relating TPR to Blood Flow. What does the relationship show?
TPR = (Pa - Pv)/ Qt Or. R = P/Q
This relationship explains that a change in resistance through vasoconstriction causes an increase in BP and vice versa in order for CO to remain constant.
What are the main metabolites that bind receptors to increase Vasodilation?
CO2, H+ and lactic acid
How does the body compensate to restore RAP back to normal after a rise from venodilation?
- Venoconstrict - adjust tone to restore it back to set-point
- Positive Inotropy - generate a new set point that’s closer to original RAP (by lowering RAP)
When localizing an MI, what leads will show myocardial injury to the INFERIOR side of the heart and what coronary vessel might be occluded?
- Leads II, III and aVF show abnormal complexes (ST elevation, T inversion, new Q waves)
- Right Coronary Artery might be occluded
Name the artery that may be occluded and the leads that may indicate abnormal complexes where anterior (septal and apical) region of the heart is injured.
- Left Anterior Descending Artery may be occluded leading to injured anteroseptal/apical regions of the heart.
- Leads V1 - V4 may show these abnormal complexes of an MI.
What leads are affected if the LATERAL side of the heart is affected and what coronary artery occlusion might have led to this myocardial injury?
- Leads V5, V6, I, and aVL may indicate damage to the anterolateral part of the heart.
- The Left Circumflex Artery may be occluded.
Name the leads that are affected if the POSTERIOR side of the heart features a tall R-wave and T-inversion on the ECG. What coronary vessel might be occluded to lead to these findings?
- Leads V1 and V2 may indicate a tall R-wave.
2. The Right Coronary Artery may be occluded.
Rank the order of Adrenergic receptor affinity for NE at…
- Low dose
- high dose
- A1 > B1»_space; B2
2. A1 and B1
Rank the order for affinity to Adrenergic receptors for Epinephrine at the following dosages.
- High Dosage
- Low Dosage
- A1 and B1
2. B1 and B2
What adrenergic drug would a physician avoid to treat an asthmatic patient with low cardiac output?
Avoid Propanolol. This is a NON-SPECIFIC beta blocker that may elicit the adverse effect of bronchoconstriction, compromising breathing.
What happens to preload in the heart under the following scenarios:
- Patient is administered NorEpi at LOW DOSE.
- A patient, after vigorous exercise is given Albuterol
- Preload INCREASES due to vaso-and-veno-constriction that increases BP.
- Preload DECREASES due to Vasodilation in skeletal muscles, therefore reducing BP (B2 Agonist)
What is the function of the Golgi Tendon Organ, how does it signal the CNS, and what would occur under high stress?
- GTO (in tendon) detects stress (stretch/tension)
- It reports via 1B Afferent Fibers
- Under high stress, CNS signals A-motor efferent to inhibit agonist and stimulate antagonist muscles (both IPSILATERAL).
What is the function of the Muscle Spindle, how does it signal the CNS, and how does the CNS send feedback?
- Spindles sense “Change in length” and “Rate of Length Change”
- It signals the CNS via
- 1A afferents (send change in length)
- 2A afferents (relay static length) - CNS sends back signals via Gamma Motor efferent fibers.
Within the muscle spindle, what do the following detect:
- Chain Fibers
- Bag Fibers
- Chain - Detects Static Length
2. Bag - Detects Change in Length
What 3 Scenarios trigger increased O2 Demand for the heart?
- Increased Wall Stress (inc. preload from blood)
- Heart Rate (works faster)
- Contractility (squeeze harder)
Describe at least 3 aspects that might differentiate Angina from a Myocardial Infarction.
- Angina is episodic upon exertion (goes away after exercise)
- Infarction can occur from cardiac cell necrosis
- MI can result from a completely occluded vessel
- Increased Troponin I and T levels signal MI
- Angina can be treated with nitroglycerin (vasodilator), Beta blockers and Ca channel blockers (Amlodipine) to decrease HR and O2 demand, respectively.
Name 3 signs/symptoms to look for in diagnosing for MI?
- High Troponin Levels
- Radiating pain in the sternum, neck, left shoulder and arm.
- SOB (dyspnea)
- Syncope (sudden drop in BP)
- Nausea, palpitations, diaphoresis
What are the normal time ranges for each of the following ECG intervals?
- PR interval
- QRS Complex
- QT interval
- Start of P to 1st deflection of QRS:120-200 ms or 3-5 small boxes
- Start of QRS to end of T-wave: <120 ms or <3 small boxes
- Encompasses the whole QRS-complex: 350-420 ms
