Cardiac Physiology Basics and ECG Analysis

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Questions and Answers

What is the primary role of the AV node in the heart?

It directly stimulates the Purkinje fibers.

It regulates heart rate through hormonal control.

It initiates atrial contraction.

It acts as a gatekeeper to control ventricular depolarization. (correct)

Which wave is responsible for ventricular repolarization on an ECG?

QRS complex

P wave

ST segment

T wave (correct)

What is the normal heart rate range for junctional bradycardia according to the content?

100 – 120 beats/min

20 – 40 beats/min

60 – 100 beats/min

40 – 60 beats/min (correct)

Which heart sound is associated with the closure of the atrial valves?

S1 or 'lub' Signup and view all the answers

When interpreting an ECG, how is the heart rate calculated from the QRS complex?

Counting QRS complexes in 10 seconds and multiplying by 6 Signup and view all the answers

Which type of shock is characterized by the heart's failure to pump blood effectively?

Cardiogenic shock Signup and view all the answers

Which of the following is NOT a clinical symptom associated with shock?

Increased urine production Signup and view all the answers

Septic shock is primarily caused by which of the following?

Systemic infection Signup and view all the answers

Which cytokines are commonly released during septic shock?

IL-1, IL-6, TNF Signup and view all the answers

What is a common symptom related to hypovolemic shock after significant trauma?

Decreased blood pressure Signup and view all the answers

What is the primary role of the sinoatrial node in the heart?

To generate electrical impulses Signup and view all the answers

During ventricular systole, what occurs in the heart?

Blood is ejected from the left and right ventricles Signup and view all the answers

What can result from a failure of the sinoatrial node?

AV node takes over the pacemaker function Signup and view all the answers

What is the normal weight range of the heart in males?

300 – 350 g Signup and view all the answers

Which of the following is NOT a major disease affecting the heart?

Hypertrophic cardiomyopathy Signup and view all the answers

What is the normal wall thickness of the left ventricle?

1.3 – 1.5 cm Signup and view all the answers

What causes blood to flow from the left atrium into the left ventricle during diastole?

Lower pressure in the ventricles than the atria Signup and view all the answers

Which of the following is TRUE about the myocytes in the heart?

They comprise 25% of the total number of cells but 90% of heart mass Signup and view all the answers

What condition is characterized by the heart's inability to pump sufficient blood through the body?

Congestive heart failure Signup and view all the answers

Which symptom is NOT typically associated with congestive heart failure?

Increased appetite Signup and view all the answers

What is a primary cause of heart failure related to the amount of blood the heart is required to pump?

Volume overload Signup and view all the answers

Which treatment method is NOT typically employed for managing heart failure?

Increased fluid intake Signup and view all the answers

What is the result of right ventricular hypertrophy caused by chronic obstructive pulmonary disease?

Congestive heart failure Signup and view all the answers

Which term describes the dilation of the heart due to volume overload?

Eccentric hypertrophy Signup and view all the answers

What is a common consequence of the left ventricle working harder to overcome increased pressure in the aorta?

Left ventricular hypertrophy Signup and view all the answers

What condition occurs if large ventricular septal defect (VSD) leads to a reversal of shunt?

Eisenmenger’s syndrome Signup and view all the answers

Which of the following symptoms is associated with right-sided heart failure?

Hepatomegaly Signup and view all the answers

Which statement accurately describes the septum wall formation in atrial septal defect (ASD)?

It leads to a left-right shunt but typically has less severe consequences than VSD. Signup and view all the answers

What happens if the ductus arteriosus does not close after birth?

Blood flows from the aorta into the lungs, increasing workload on the heart. Signup and view all the answers

Which clinical feature is commonly associated with patent foramen ovale (PFO)?

Paradoxical embolus leading to stroke Signup and view all the answers

What is a characteristic of Tetralogy of Fallot (ToF)?

It causes cyanosis through a right-to-left shunt. Signup and view all the answers

Study Notes

Basics

Normal heart weight: females (250-300 g); males (300-350 g).
Wall thickness: right ventricle (0.3-0.5 cm); left ventricle (1.3-1.5 cm).
90% of the heart's mass is made up of myocytes (heart muscle cells), but they only make up 25% of the cells.
Heart function relies on the conduction of electrical impulses.
The sinoatrial node (SA node) is the pacemaker of the heart, located in the right atrium.
The SA node discharges at 70–80 times/minute and is innervated by vagal and sympathetic nerve fibers.
The AV node is a "gatekeeper" that prevents too fast depolarization of the heart.

ECG

Normal ECG strip: 10 seconds
To calculate heart rate: multiply ventricular depolarization (QRS) count in 10 seconds by 6
Interpretation: check if the P wave precedes the QRS complex and analyze the ST waves.

Heart Sounds

First heart tone ("lub"): produced by the vibration of blood against closed atrial valves, marking the start of systole.
Second heart tone ("dub"): caused by the closure of the aortic and pulmonary valves at the end of systole.
S2 can sometimes be split into P2 (pulmonary valve sound) and A2 (aortic valve sound) during inspiration (inhaling).

Congestive Heart Failure

Characterized by the heart's inability to pump sufficient blood throughout the body.
Caused by factors that impair heart function: myocardial infarction, hypertension, arrhythmias, valve defects, pulmonary hypertension, and so forth.
Main cause: volume overload, requiring the heart to pump more blood.
Symptoms: shortness of breath during exercise or at rest, fatigue, pulmonary edema, peripheral edema, ascites, nocturia (urinating at night), and jugular vein distension.
Treatment: address underlying causes, weight reduction, fluid management, sodium restriction, and medication (antihypertensives, diuretics, beta blockers, and antiarrhythmics).

General Causes of Heart Failure

Left side of the heart:
- Hypertensive heart disease: left ventricle works harder to overcome increased pressure in the aorta, leading to left ventricular hypertrophy.
- Coronary heart disease.
- Arrhythmias.
Right side of the heart:
- Cor pulmonale: right ventricle hypertrophy or dilation due to impaired lung perfusion.
  - Acute cor pulmonale: pulmonary embolism (PE).
  - Chronic cor pulmonale: chronic obstructive lung disease, lung tissue loss (tuberculosis, cancer surgery).
- Mechanism: right ventricle works harder to pump blood through the lungs.
- The heart compensates until it fails.

Shock

Three most frequent types of shock:
- Cardiogenic shock: heart failure to pump blood (MI, arrhythmias, PE, heart tamponade).
- Hypovolemic shock: blood volume loss (bleeding, burns, trauma).
- Septic shock: systemic infection (mainly gram-negative organisms – endotoxic shock).
Other types of shock: anaphylactic shock and neurogenic shock following spinal cord injury.

Clinical Symptoms of Shock

Anxiety, restlessness, disorientation.
Hypotension.
Rapid pulse (tachycardia).
Cool, clammy, mottled skin.
Decreased urine production (oliguria).
Rapid breathing (hyperventilation).

Blood Circulation Before and After Birth

Before birth, oxygenation occurs through the placenta, not the lungs.
Fetal blood bypasses the lungs through the foramen ovale between the right and left atria.
Shortly before/after birth, the foramen ovale closes.
Blood from the pulmonary artery takes a shortcut through the ductus arteriosus to the aorta.

Atrial Septal Defect (ASD)

A left-right shunt occurs when the septum wall does not form properly.
Consequences are usually less severe than ventricular septal defects, with no symptoms before age 30.
Results in right heart hypertrophy eventually.
Systolic murmur!
Paradoxical embolus: thrombosis can travel from the right heart to the left heart and cause a stroke if the foramen ovale doesn't close (patent foramen ovale - PFO).

Patent Ductus Arteriosus (PDA)

In the fetus, blood from the right heart bypasses the lungs through shortcuts (foramen ovale and ductus arteriosus) directly to the aorta.
After birth, the ductus arteriosus usually closes within 15 hours.
If it doesn't close, blood flows from the aorta (with higher blood pressure) into the lungs.
This increases blood flow through the lungs and decreases oxygenated blood in the aorta.
The heart has to work harder.
Clinical feature: machine-like sound over the heart.
Right-to-left shunts causing cyanosis.

Tetralogy of Fallot (ToF)

RIGHT-TO-LEFT SHUNT!
A large VSD will lead to right heart hypertrophy and eventually a reversal of the shunt.
Deoxygenated blood flows from right to left, causing cyanosis (Eisenmenger's syndrome).
Prognosis is very poor if this occurs.

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Description

Test your knowledge on the basics of cardiac physiology, including heart weight, wall thickness, and the roles of key cardiac structures such as the SA and AV nodes. Additionally, this quiz covers the interpretation of ECG strips and heart sounds involved in cardiac cycles. Perfect for students studying cardiology or health sciences.