EKG's and Cardiac System

What makes up the cardiovascular system?

Heart, great vessels, veins, and arteries.

Where is the heart located?

In the mediastinum, behind the sternum.

How many chambers does the heart have?

Four: right atrium, left atrium, right ventricle, and left ventricle.

What is the myocardium?

The muscular tissue of the heart.

What is the pericardium?

A thin sac surrounding the heart.

What is the function of the coronary arteries?

Supply blood to the myocardium.

What does the right atrium receive?

Deoxygenated blood from the superior and inferior vena cava.

What does the left atrium receive?

Oxygenated blood from the pulmonary veins.

Which veins carry oxygenated blood?

Pulmonary veins.

Which arteries carry deoxygenated blood?

Pulmonary arteries.

Which valve separates the right atrium and right ventricle?

Tricuspid valve.

Which valve separates the left atrium and left ventricle?

Mitral valve.

Which valve allows blood to leave the right ventricle?

Pulmonic valve.

Which valve allows blood to leave the left ventricle?

Aortic valve.

What is pulmonary circulation?

Right ventricle pumps deoxygenated blood to the lungs, which returns oxygenated blood to the left atrium.

What is systemic circulation?

Left ventricle pumps oxygenated blood to the body, which returns deoxygenated blood to the right atrium.

What do veins do?

Carry blood back toward the heart.

What do arteries do?

Carry blood away from the heart.

What is systole?

Contraction phase of the heart.

What is diastole?

Relaxation and filling phase of the heart.

What is the normal adult heart rate?

60–100 beats per minute.

What instrument measures systemic blood pressure?

Sphygmomanometer.

What is the upper blood pressure reading?

Systolic blood pressure.

What is the lower blood pressure reading?

Diastolic blood pressure.

What is the ideal blood pressure listed in the slides?

120/80 mm Hg.

What is mean arterial pressure (MAP)?

The average driving pressure propelling blood from the left ventricle to the right atrium.

What does MAP most closely relate to?

Overall adequacy of tissue perfusion.

What is the normal MAP range in the slides?

80–100 mm Hg.

What does a MAP below 80 mm Hg indicate according to the slides?

Hypotension.

What does a MAP above 100 mm Hg indicate according to the slides?

Hypertension.

What is the MAP formula?

MAP = (Systolic BP + 2 × Diastolic BP) ÷ 3.

What is the MAP of a patient with BP 120/80?

93.3 mm Hg.

What is pulse pressure?

The difference between systolic and diastolic blood pressure.

What is the pulse pressure formula?

Systolic BP − Diastolic BP.

What does increased pulse pressure usually indicate?

Increased stroke volume or cardiac output.

What does decreased pulse pressure usually indicate?

Decreasing stroke volume or cardiac output.

What factors directly influence blood pressure?

Stroke volume, blood volume, arterial compliance, and arterial resistance.

What is stroke volume (SV)?

The volume of blood ejected during a single ventricular contraction.

What is cardiac output (CO)?

The amount of blood ejected from the heart in one minute.

What is the cardiac output formula?

CO = Stroke Volume × Heart Rate.

What are the three determinants of cardiac output?

Ventricular preload, ventricular afterload, and myocardial contractility.

What is ventricular preload?

The degree to which myocardial fibers are stretched before contraction.

When does preload occur?

During end-diastole, before ventricular contraction.

What reflects ventricular preload?

Ventricular end-diastolic pressure and ventricular end-diastolic volume.

What is the Frank-Starling principle?

Within limits, greater myocardial fiber stretch during diastole produces a stronger contraction during systole.

What is ventricular afterload?

The force against which the ventricles must work to pump blood.

What best reflects ventricular afterload?

Arterial systolic blood pressure.

What directly influences afterload?

Blood volume and viscosity, peripheral vascular resistance, and total cross-sectional vascular area.

What is myocardial contractility?

The strength of myocardial contraction.

What happens when contractility decreases?

Stroke volume and cardiac output decrease, reducing tissue perfusion and oxygen delivery.

What is ejection fraction (EF)?

The percentage of blood pumped from a ventricle during a single contraction.

What is the average healthy ejection fraction in the slides?

60–70%.

What is end-diastolic volume (EDV)?

The volume of blood in the ventricles after filling during diastole.

What is end-systolic volume (ESV)?

The volume of blood remaining in the ventricles after systole.

What is the ejection fraction formula?

EF = Stroke Volume ÷ End-Diastolic Volume × 100.

What is pulmonary vascular resistance (PVR)?

The resistance against which the right ventricle contracts in the pulmonary circulation.

What does hypoxemia do to pulmonary blood vessels?

Causes pulmonary vasoconstriction.

What happens to PVR during hypoxic pulmonary vasoconstriction?

PVR increases.

What can chronically increased PVR cause?

Pulmonary hypertension and right ventricular failure.

What is the normal cardiac electrical conduction pathway?

SA node → AV node → Bundle of His → Right and left bundle branches → Purkinje fibers.

What is the primary pacemaker of the heart?

Sinoatrial (SA) node.

Where is the SA node located?

Right atrium.

What is automaticity?

The ability of cardiac cells to spontaneously generate electrical signals.

What is the normal firing rate of the SA node?

60–100 beats per minute at rest.

What does sympathetic stimulation do to heart rate?

Increases heart rate.

What does parasympathetic or vagal stimulation do to heart rate?

Slows heart rate.

What is the function of the AV node?

Delays the electrical impulse to allow more complete ventricular filling.

How long is the approximate AV node delay described in the slides?

0.1 seconds.

What is the backup pacemaker if the SA node fails?

AV junction.

What is the typical AV junction escape rate?

40–60 beats per minute.

What is the function of Purkinje fibers?

Distribute electrical impulses rapidly throughout the ventricular myocardium.

What is an ECG or EKG?

An indirect measurement of the electrical activity of the heart.

What does an ECG measure?

Electrical activity of the heart.

Does an ECG measure the pumping ability of the heart?

No.

What can an ECG help identify?

Myocardial infarction, ventricular hypertrophy, and dysrhythmias.

What is a 12-lead ECG?

An ECG that provides 12 different views of the heart's electrical activity.

How many limb leads are used in a standard 12-lead ECG?

Six extremity leads.

How many chest leads are used in a standard 12-lead ECG?

Six chest leads.

What does the P wave represent?

Atrial depolarization.

What does the QRS complex represent?

Ventricular depolarization.

What does the T wave represent?

Ventricular repolarization.

What does the horizontal axis of ECG paper represent?

Time.

What does the vertical axis of ECG paper represent?

Voltage or amplitude.

How much time does one small ECG box represent?

0.04 seconds.

How much time does one large ECG box represent?

0.20 seconds.

How many small boxes are in one large ECG box?

Five.

What does an upward deflection of 10 ECG boxes represent?

1 mV.

How do you calculate heart rate with a regular rhythm?

300 ÷ number of large boxes between QRS complexes.

How do you calculate heart rate with an irregular rhythm?

Count QRS complexes in a 6-second strip and multiply by 10.

What is the normal PR interval?

0.12–0.20 seconds.

What is the normal QRS duration?

Less than 0.12 seconds.

What does an isoelectric ST segment mean?

The ST segment is flat and at the baseline.

What are the characteristics of normal sinus rhythm?

Rate 60–100 bpm, regular rhythm, normal P waves followed by QRS complexes, PR interval 0.12–0.20 seconds, and QRS less than 0.12 seconds.

What is sinus bradycardia?

A sinus rhythm with a heart rate below 60 beats per minute.

What are the ECG characteristics of sinus bradycardia?

Regular rhythm, normal P waves, PR interval 0.12–0.20 seconds, and QRS less than 0.12 seconds.

What is sinus tachycardia?

A sinus rhythm with a heart rate of 100–150 beats per minute.

What are the ECG characteristics of sinus tachycardia?

Regular rhythm, normal P waves, PR interval 0.12–0.20 seconds, and QRS less than 0.12 seconds.

What are common causes of sinus tachycardia?

Fever, pain, hypoxemia, hypovolemia, hypotension, sepsis, heart failure, suctioning, beta-agonist bronchodilators, and caffeine.

Why can sinus tachycardia cause myocardial ischemia?

It increases myocardial oxygen demand and decreases diastolic filling time.

What is sinus dysrhythmia?

A sinus rhythm that is irregular but otherwise meets normal sinus rhythm criteria.