Cardiac Physiology Flashcards

Flashcards reviewing cardiac physiology lecture notes.

How do anesthetic agents affect the cardiovascular system?

Every anesthetic agent has either a direct or an indirect effect on the cardiovascular system.

What hemodynamic variables are commonly affected by agents during the perioperative period?

Heart rate, rhythm, blood pressure, or cardiac output.

By what mechanism do drugs used for rhythm and rate control act?

Modulating Na+, K+, and Ca+2 currents.

What is the role of intracellular calcium in the myocardium?

It is a key mediator in coupling electrical excitation to mechanical contraction and is an important determinant of the contractile state of the myocardium.

How does blood flow in relation to pressure?

Blood tends to flow from areas of high pressure to areas of lower pressure.

What determines the opening and closing of cardiac valves?

The pressure gradients across those valves at any point in time.

Is the pericardium essential for survival?

No, normal cardiac function can occur in the absence of the pericardium.

What are the physiological functions of the pericardium?

1. Reduces friction between the heart and surrounding structures. 2. Limits acute dilatation of cardiac chambers. 3. Provides a barrier to infection. 4. Limits excessive movement of the heart in the chest cavity.

What substances does the metabolically active pericardium secrete and what are their effects?

Prostaglandins that affect coronary artery tone and cardiac reflexes.

How is the pericardium innervated and what can result from its inflammation or manipulation?

Via the vagus nerve, phrenic nerve, and sympathetic trunks. Inflammation or manipulation may produce pain or vagally mediated reflexes.

What is a functional syncytium in the context of cardiac muscle?

Cardiac muscle cells are electrically connected through intercalated discs, allowing them to contract simultaneously.

How does the structure of myocardial fibers differ from skeletal muscle?

Myocardial fibers have a more branching, interconnected structure, with gap junctions facilitating the conduction of the action potential from one cell to another.

What are the differences in the sarcomeres of myocardial cells compared to skeletal muscle cells?

Myocardial sarcomeres contain a higher concentration of mitochondria due to the heart's high metabolic rate and have a rich capillary blood supply (one capillary per fiber) that allows for efficient diffusion and perfusion.

What is the structure and function of the fibrous skeleton of the heart?

Composed of 4 fibrous rings (around the MV, TV, the pulmonary trunk, and the aortic orifice) and the membranous portions of the interatrial, interventricular, and atrioventricular septa. It provides attachment points for valve leaflets and cusps, framework for attachment of myocardial fibers, acts as an electrical insulator, and provides a passageway for the AV Bundle.

What are the different types of atrial septal defects (ASDs)?

Secundum defect (75%) (central), Primum defect (above AV valves), Sinus venosus defect (at either the SVC or IVC junction), Unroofed coronary sinus

What is the structure of the interventricular septum?

Composed of a membranous septum (upper and posterior) and a muscular septum (anterior).

What are the components of the aortic valve?

Part of the aortic root (annulus, AV cusps, the sinuses of Valsalva, and the proximal ascending aorta). Trileaflet semilunar valve. Left, right, and non-coronary cusps. Right and Left cusps give rise to RCA and Left Main coronary artery.

What are the Atrioventricular (AV) valves?

Tricuspid valve.

What is the cardiac conduction system?

Sinoatrial (SA) node, Atrioventricular (AV) node, Atrioventricular (AV) bundle (bundle of His), Right and left bundle branches, Purkinje fibers

What are the segments, intervals, and waves of an ECG?

P wave, QRS complex, T wave, P-R interval, S-T segment

What are the two components of Neural Control of Cardiac Function?

Parasympathetic (Vagus nerves) and Sympathetic Chain (T1-T4)

What is the effect of PNS activation on the heart?

The PNS acting via Ach and muscarinic receptors (via vagal nerve) reduces HR, AV node conduction, and contractility.

What is the effect of SNS stimulation on the heart?

The SNS acting through adrenergic receptors (via norepinephrine) has positive ionotropic, chronotropic, and lusitropic effects on the heart.

Name the three hormonal control functions of cardiac function.

Atrial Natriuretic Peptide (ANP), B-type Natriuretic Peptide (BNP), and Adrenomedullin

What actions do ANP and BNP have on the myocardium?

They help the myocardium by inducing diuresis, natriuresis, and vasodilation

What is the action of Adrenomedullin on the myocardium?

Acts by increasing cAMP levels, and has positive ionotropic and chronotropic effects, as well as vasodilation

What ionic content exist outside of the cell?

Na+, Cl-

What ionic content exist inside of the cell?

K+

What are the phases of a cardiac action potential?

Phase 0 (depolarization), Phase 1 (Na channels close), Phase 2 (plateau), Phase 3 (rapid repolarization), Phase 4 (resting potential)

What are the classes of drugs affecting the cardiac action potential?

Class 1 (Na+ channel blocker), Class 2 (β-blocker), Class 3 (K+ channel blocker), Class 4 (Ca2+ channel blocker)

What role does Calcium play in cardiac function?

It is one of the key ions involved in cell membrane depolarization and action potential propagation. It is the major ion involved in excitation-contraction coupling and muscle contraction.

What are the major ionic movements during excitation-contraction coupling in cardiac muscle?

Influx of Ca2+ from the interstitial fluid during excitation triggers the release of Ca2+ from the sarcoplasmic reticulum (SR). Free cytosolic Ca2+ activates contraction of the myofilaments (systole). Relaxation (diastole) occurs as a result of uptake of Ca2+ by the SR and extrusion of intracellular Ca2+ by Na+-Ca2+ exchange.

What is the relation of cardiac sarcoplasmic reticulum to surface membrane and myofibrils?

The SRL and C overlie the myofilaments; they are shown separately for illustrative purposes.

What are the steps in actin-myosin dependence on Ca2+-troponin binding for tension development?

REST, (Ca++) = 0. CONTRACTION, (Ca++) = 1 μM

What parameters determines the frank starling curve performance of the heart?

Preload- venous return, end-diastolic volume, afterload - systemic vascular resistance and contractility

What occurs during ventricular filling?

Mitral valve opens

What occurs during Isovolumetric contraction?

Mitral valve closes

What occurs during Ventricular ejection?

Aortic valve opens

What occurs during Isovolumetric relaxation?

Aortic valve closes

What hemodynamic equations determine the mean arterial pressure?

MAP = CO× SVR or MAP = 2/3 diastolic pressure + 1/3 systolic pressure

What are the methods for determining CO?

Thermodilution, Fick Method, Echocardiography

List the normal hemodynamic values.

Cardiac index = 2.4 L per minute, Cardiac output = 5-7 L per minute, Stroke volume = 70-90 mL (1 mL/kg), MAP = 60-90 mm Hg, CVP = 5-10 mm Hg, SVR 800-1,200 dyne/s/cm5

Acute inferior myocardial infarction ECG characteristics

ST elevation in the inferior leads II, III and aVF and reciprocal ST depression in the anterior leads.

Old inferior myocardial infarction ECG characteristics

a Q wave in lead III wider than 1 mm (1 small square),a Q wave in lead aVF wider than 0.5 mm and a Q wave of any size in lead II

Acute anterior myocardial infarction ECG characteristics

ST elevation in the anterior leads V1-6, I and aVL and reciprocal ST depression in the inferior leads

Acute posterior myocardial infarction ECG characteristics

the mirror image of acute injury in leads V1 -3, usually associated with inferior and/or lateral wall MI

Atrial flutter ECG characteristics

A characteristic 'sawtooth' or 'picket-fence' waveform of an intra-atrial re-entry circuit usually at about 300 bpm.

Hyperkalaemia ECG features

small or absent P waves, atrial fibrillation, wide QRS, shortened or absent ST segment, wide, tall and tented T waves, ventricular fibrillation

Hypokalaemia ECG features

small or absent T waves, prominent U waves, first or second degree AV block, slight depression of the ST segment

Sinus tachycardia ECG features

P wave rate greater than 100 bpm

Right Bundle Branch Block ECG features

wide QRS, more than 120 ms (3 small squares), secondary R wave in lead V1, slurred S wave in lateral leads and T wave changes in the septal leads

Give different criteria for Left ventricular hypertrophy (LVH)

Sokolow + Lyon , Cornell criteria, Framingham criteria, Romhilt + Estes

ECG features for Atrial Premature Beat

an abnormal P wave, occurs earlier than expected, followed by a compensatory pause - but not a full compensatory pause

Define Atrial Bigeminy

each beat is followed by an atrial premature beat

Give features of Junctional Rhythms

May be before, during or after the QRS, May be abnormal in size and shape

Define Atrial fibrillation with rapid ventricular response

Irregularly irregular ventricular rhythm.

Paroxysmal Supraventricular Tachycardia (PSVT) defining features

Are not easily seen, because they are buried in the T waves;Difficult to determine due to the rapid rate and poorly distinguished P waves

ECG criteria for Ventricular tachycardia

Wide (>.12) and bizarre appearance

Ventricular bigeminy defintion

a ventricular premature beat follows each normal beat

Idioventricular defining features

Typically 20-40; Often absent P wave

First Degree Block defining features

PR Interval >.20 Before each QRS

Second Degree Block: Type I

Progressive lengthening of the PR until a QRS is dropped

Second Degree Block: Type II features

Intervals will remain constant unrelated with QRS; Cause organic lesions, May progress to 3rd degree!, Prepare level venticule

Third Degree Block (complete)

PR No relationship between the P and R; Atrial rate 603100

Ventricular pacemaker features

Pacing spikes (best seen here in V4 - V6); The paced QRS complexes are abnormally wide