Pulse and Heart Function Basics

Pulse

• Pulse is the wave of blood forced through arteries by left ventricle contraction.
• Alternating expansion and recoil of arteries during each cardiac cycle creates the pulse wave.

Introduction

• The heart's conduction begins with an electrical impulse in the sinoatrial (SA) node of the right atrium.
• In adults, the SA node initiates electrical impulses 60-100 times per minute.
• This impulse quickly travels through the conduction system, causing heart muscle fibers to contract synchronously.

Pulse Definitions

• Waves of blood: Blood forced through arteries by left ventricle contraction.
• Arterial expansion/recoil: Blood waves created by alternating expansion and recoil of arteries during the cardiac cycle.

Physiology and Regulation

• Blood circulates continuously, controlled by cardiac centers in the medulla of the brain stem.
• Sympathetic or parasympathetic systems regulate heart rate.
• Sensory impulses from the heart (e.g., aortic arch stretch from increased blood volume) trigger a reflex slowing of heart rate via the parasympathetic nervous system.

Cardiac Output

• Stroke volume (SV): Amount of blood ejected per heartbeat (70 ml).
• Cardiac output (CO): Amount of blood pushed by ventricles per minute (CO = SV x Heart Rate).
• Increased blood volume tends to decrease heart rate.
• Decreased blood volume will increase heart rate.
• Normal circulatory blood flow is approximately 70-72ml of blood entering the aorta with each ventricular contraction.
• The aorta expands with each ejection, creating a pulse wave that travels to peripheral arteries for palpation.

Pulse Characteristics

• Rate: Number of pulsations felt over an artery per minute.
• Rhythm: Time intervals between pulse beats.
  • Regular rhythm: Equal intervals between beats
  • Irregular rhythm: Interrupted intervals or early/late/missing beats (arrhythmia/dysrhythmia).
• Volume/Amplitude/Strength: Reflects blood ejected, blood's force against arterial walls, and vascular condition.
  • Pulse strength is graded as normal, thready, weak, or bounding.

Factors Affecting Pulse Rate

• Age: Female pulse rate slightly higher than male pre-menopause.
• Sex: Females (pre-menopause) tend to have slightly higher pulse rates than males.
• Exercise/Muscular Activity: Exercise increases pulse rate; rest and sleep decrease it.
• Temperature: Pulse rate increases about 10 beats per minute with each degree of temperature elevation.
• Stress/Emotions: Stress increases sympathetic stimulation, increasing heart rate.
• Medications: Positive chronotropics (e.g., atropine) increase pulse rate; negative chronotropics (e.g., digitalis) decrease it.
• Hemorrhage: Blood loss increases sympathetic stimulation and pulse rate.
• Position Changes: Standing/sitting pulse rate higher than lying down.
• Pulmonary Conditions: Conditions affecting oxygenation increase pulse rate.
• Disease Conditions: Many diseases can alter pulse rate (some increase; some decrease).

Pulse Deficit

• An inefficient heart contraction disrupting pulse transmission generates a pulse deficit.
• This deficit is assessed by comparing apical and radial pulse rates to see the difference.

Pulse Assessment Methods

• Palpation: Using the tip of the middle fingers to feel for pulse rate, rhythm, and volume.
• Auscultation: Using a stethoscope to listen to the apical pulse (most accurate for irregular rhythms or difficult peripheral pulses).

Stethoscope Parts

• The stethoscope has four major parts: earpieces, binaural spring, tubing, and chest piece (which includes bell and diaphragm).

Pulse Sites

• Diagram showing various pulse sites on the body.

Pulse Abnormalities

• Tachycardia: Abnormally elevated pulse rate (over 100 beats per minute in adults).
• Bradycardia: Abnormally slow pulse rate (below 60 beats per minute in adults).
• Pulsus Bigeminus: Premature (weak) beat with a normal beat.
• Pulsus Trigeminus: Premature beat with two normal beats.
• Ventricular Tachycardia: Weak, rapid pulse (150-250 bpm), originating from a hyper-excitable ventricular focus.
• Atrial Fibrillation: Irregular, weak pulse with a pulse deficit, originating from rapid multiple atrial firing.

This quiz explores the fundamentals of pulse and heart physiology. It covers the mechanics of blood flow, the role of the sinoatrial node, and the regulatory systems governing heart rate. Test your knowledge on how these elements work together to maintain circulation.