Cardiac

Topics: Heart, Blood, Artery Pages: 27 (5913 words) Published: June 25, 2013
Cardiovascular Anatomy & Physiology

I. Structures and Functions

Heart Muscle
* Has 3 layers (epicardium, myocardium, and endocardium) and a surrounding sac called the pericardium * Location: In the mediastinum, above the diaphragm, and is surrounded on both sides by lung * Shape: Resembling triangle, with base parallel to the right edge of the sternum

Heart Chambers
* The right side of the heart is a low pressure system and the left side is a high pressure system and each side has an atrium and ventricle. * Here is the Right Atrium (RA,) Right Ventricle (RV,) Left Atrium (LA,) Left Ventricle (LV,) and the Medial Wall separating the RV and LV. Valves

* The heart contains the two atrioventricular valves (AV) and two semilunar valves as well as the Chordae Tendineae and the Papillary Muscles * AV valves are Tricuspid Valve and Mitral Valve

* Semilunar valves are Pulmonic Valve and Aortic Valve
* Chordae Tendineae and Papillary Muscles work together to prevent valve leaflets from turning inside out.

* Normally, the cavity between the pericardial layers contains 10-30mL of serous fluid * A pericardial effusion occurs if additional blood or fluid collects in this space. If the amount of fluid continues to increased and cardiac chamber filling is impeded, cardiac tamponade results * VAGUS – major PNS innervation of the heart

* CALCIUM – is the main cation affecting electrical stimulation of the heart * THRESHHOLD – is the stimulus that changes the resting membrane * COLD – is the condition that slows down blood flow

II. Conduction System

Cellular Electrophysiology of the Heart
* The fast, more organized tracts include the SA Node, AV junction (AV node and the Bundle of His,) and Purkinje fiber. * SA and AV Nodes
* SA Node is the major pacemaker of the heart. It keeps intrinsic heart rate at 60100 bpm * The AV node receives impulse from atria and slows it down before sending to ventricles. This slowing is done in order to allow time for ventricular filling from the atrial contraction. Is capable of generating its own impulse if doesn’t receive one (Automaticity.) Intrinsic rate is 40-60 bpm.

Bundle of His
* Bundle of His is point where impulse divides into the right and left bundle branches and further proceeds on to the Purkinje fibers * A blockage in a bundle branch shows up on an ECG
* Bundle of His and Bundle Branches can together act as an escape pacemaker for the heart with an intrinsic rate of 20-40 bpm.

Speed Sinus Rate:
* Atropine

Slow Sinus rate:
* Beta blocker
* CCB
* Digitalis

Speed AV conduction
* Atropine
* Isoproterenol (Isuprel)

Suppress Atrial Arrythmias
* Quindipine
* Procainamide (Pronestyl)
* Sotalol
* Amiodarone
* CCB works for some

Slow AV conduction
* Digitalis
* Beta blocker
* CCB
* Adenosine
* Vagal Maneuver

Suppress Ventricular Arrhythmias
* Lidocaine
* Procainamide
* Bretylium
* Quinidine
* Amiodarone
* Sotalol
* Magnesium

QT interval prolongation contraindication Meds page 21 (notes)

III. Blood Supply and Systemic Circulation

In this topic we look at the coronary arteries. These supply oxygenated blood to the heart. We learn the importance of knowing which arteries supply the different sections of the heart so that we can pull clues about potential complications if and when they occur with a patient.

Coronary Arteries
* There are two main ones.
* They supply oxygenated blood to the heart.
* The main or “dominant” one of the two is usually the right coronary artery.

Right Coronary Artery
* Supplies blood to the right atria, the right ventricle, most of the conduction system, and to the inferior and posterior sections of the left ventricle * Occlusion can result in inferior or posterior MI, bradycardia-type dysrhythmias...
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