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CardiacCycle,ECG&HeartHemodynamics

Q: What causes the heart sounds S1 ('Lub') and S2 ('Dub')?

S1 ('Lub') is generated by the sudden closure and vibration of the atrioventricular valves (Tricuspid and Mitral) at the start of ventricular systole. S2 ('Dub') is generated by the sudden closure of the semilunar valves (Aortic and Pulmonic) at the onset of ventricular diastole.

Q: What is the Wiggers Diagram and why is it important?

The Wiggers Diagram is a standard medical reference chart that synchronizes Left Ventricular pressure, Aortic pressure, Left Atrial pressure, Ventricular volume, Lead II ECG, and Phonocardiogram (heart sounds) on a shared time axis, illustrating the exact physical interplay behind every heartbeat.

Q: How does the Frank-Starling Law work?

The Frank-Starling Law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles before contraction (end-diastolic volume / preload). Increased stretch of myocardial muscle fibers aligns actin and myosin filaments more optimally, generating greater contractile force.

Explore the mechanical, electrical, and hemodynamic events of the human heartbeat in real time. Adjust heart rate, preload, contractility, and afterload to observe changes in cardiac output, ejection fraction, ventricular pressures, and heart sounds (S1 Lub and S2 Dub).

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Cardiac Cycle, ECG & Heart Hemodynamics interactive Biology simulation illustration

4-Chamber Heart & Wiggers DiagramInteractive Myocardial Wall • Realtime Lead II ECG • S1/S2 Auscultation • Frank-Starling Hemodynamics

Interactive Experiment Guide

Use this studio like a real-time biology workbench

Start with fundamental scientific principles, launch the simulation, and verify mathematical predictions against real-time outcomes.

DisciplineBiology

Simulation ModeInteractive Numeric Engine

Governing Model4-Chamber Heart & Wiggers Diagram

DeploymentIn-Browser WebAssembly / GPU

Scientific Foundation

What is cardiac cycle, ecg & heart hemodynamics?

The human cardiac cycle encompasses all mechanical and electrical events occurring from the beginning of one heartbeat to the beginning of the next. Deoxygenated blood returns via the Vena Cava to the Right Atrium, moves past the Tricuspid valve to the Right Ventricle, and is pumped into the Pulmonary Artery to the lungs. Oxygenated blood returns via the Pulmonary Veins into the Left Atrium, passes the Mitral/Bicuspid valve into the Left Ventricle, and is vigorously ejected across the Aortic valve into the systemic circulation. The cycle is tightly governed by the SA-AV electrical conduction network, the Frank-Starling mechanism (length-tension relationship), and pressure gradients mapped in the classical Wiggers Diagram.

Interactive Simulation Flow

Experiment Execution & Governing Equations

Launch the simulation workspace, adjust parameters in real time, and observe the immediate response in the telemetry and graphical indicator loops.

Cardiac Output, Ejection Fraction & Mean Arterial PressureCO = \text{HR} \times \text{SV} \quad \text{and} \quad \text{EF} = \frac{\text{SV}}{\text{EDV}} \times 100\% \quad \text{and} \quad \text{MAP} = \text{DBP} + \frac{1}{3}(\text{SBP} - \text{DBP})

Frequently Asked Questions

Cardiac Cycle, ECG & Heart Hemodynamics FAQ

4 Answers

What is the difference between systole and diastole?

Systole refers to the phase of contraction when the heart chambers pump blood out (atrial systole pumps blood into the ventricles, and ventricular systole ejects blood into the pulmonary artery and aorta). Diastole is the relaxation phase during which the chambers refill with blood.

What causes the heart sounds S1 ('Lub') and S2 ('Dub')?

What is the Wiggers Diagram and why is it important?

How does the Frank-Starling Law work?

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Curriculum Mastery

Learning Objectives

Differentiate the 6 key mechanical phases of the cardiac cycle (Late Diastole, Atrial Systole, Isovolumetric Contraction, Rapid Ejection, Isovolumetric Relaxation, Rapid Inflow).
Correlate Lead II ECG waveforms (P wave, QRS complex, T wave) with mechanical events in the Wiggers diagram.
Calculate Cardiac Output (CO), Stroke Volume (SV), Ejection Fraction (EF), and Mean Arterial Pressure (MAP) under varying physiological conditions.
Identify the origins of the primary heart sounds (S1 caused by AV valve closure, S2 caused by semilunar valve closure) and pathological murmurs.
Apply the Frank-Starling Law to explain how changes in end-diastolic volume (preload) modulate myocardial contractility and stroke volume.

Practical Context

Real-World Applications

Clinical Cardiology & Electrocardiography: Diagnosing arrhythmias, AV conduction blocks, and myocardial infarctions from 12-lead ECG traces.
Echocardiography & Hemodynamic Monitoring: Measuring Left Ventricular Ejection Fraction (LVEF) and cardiac output in intensive care units.
Pharmacological Interventions: Assessing the impact of beta-blockers, inotropes (epinephrine, digoxin), and ACE inhibitors on cardiac workload and afterload.
Valvular Heart Disease Management: Differentiating systolic ejection murmurs in Aortic Stenosis from regurgitant murmurs in Mitral Incompetence.