What abnormalities appear on a Wiggers diagram during atrial systole in atrial fibrillation, complete atrioventricular block, and mitral or tricuspid stenosis?

Abnormalities on Wiggers Diagram During Atrial Systole

In atrial fibrillation, the atrial systole phase is completely absent on the Wiggers diagram, eliminating the "a" wave in atrial and venous pressure tracings, the A wave in mitral/tricuspid inflow Doppler, and the fourth heart sound. 1

Atrial Fibrillation

Pressure Tracings

• The "a" wave disappears from both the left atrial pressure tracing and the jugular venous pulse, as coordinated atrial contraction is lost due to chaotic atrial electrical activity 1
• Ventricular filling becomes entirely passive during early and mid-diastole, with no active atrial contribution at end-diastole 1
• The atrial pressure tracing shows only irregular fibrillatory waves instead of the normal organized "a" wave 1

Doppler Flow Patterns

• The mitral inflow A wave is absent, leaving only the E wave (early passive filling) on transmitral Doppler 1
• The tricuspid inflow A wave is similarly absent, with only passive E wave filling 1
• The E/A ratio becomes unmeasurable since A velocity is zero 1

Heart Sounds

• The fourth heart sound (S4) disappears completely, as S4 is generated by atrial contraction against a stiff ventricle 1
• Beat-to-beat variability in S1 intensity occurs due to irregular R-R intervals and variable ventricular filling 1

Hemodynamic Consequences

• Loss of the atrial "kick" reduces cardiac output by 15-25%, particularly problematic in patients with diastolic dysfunction, mitral stenosis, hypertrophic cardiomyopathy, or restrictive cardiomyopathy 1
• Left ventricular end-diastolic pressure may rise due to loss of coordinated atrial emptying 1

Complete Atrioventricular Block

Pressure Tracings

• Cannon "a" waves appear intermittently in the atrial and jugular venous pressure tracings when the atrium contracts against a closed atrioventricular valve 2
• These giant "a" waves occur randomly throughout the cardiac cycle due to AV dissociation, not synchronized with ventricular systole 2
• The atrial pressure tracing shows regular "a" waves at the atrial rate (typically 60-100 bpm), while ventricular contractions occur at the escape rhythm rate (typically 30-50 bpm) 2

ECG Correlation

• P waves are present but completely dissociated from QRS complexes, with no consistent PR interval 2
• The ventricular rhythm is regular (unlike atrial fibrillation) but slow, representing a junctional or ventricular escape rhythm 2

Doppler Flow Patterns

• Mitral and tricuspid A waves occur at irregular intervals relative to the E wave, depending on when atrial systole happens to fall in the cardiac cycle 2
• When atrial contraction occurs during ventricular systole (against closed AV valves), no forward flow is generated and cannon waves result 2
• When atrial contraction occurs during early ventricular diastole, an exaggerated A wave may appear on Doppler 2

Heart Sounds

• Variable S4 intensity or complete absence when atrial contraction coincides with ventricular systole 2
• Variable S1 intensity due to changing position of AV valve leaflets at the onset of ventricular systole 2

Mitral Stenosis

Pressure Tracings

• Elevated left atrial pressure throughout diastole, with a prominent "a" wave reflecting forceful atrial contraction against the stenotic valve 1, 3
• Prolonged pressure gradient between left atrium and left ventricle persists throughout diastole, including during atrial systole 1
• The "a" wave amplitude is increased (often >15 mmHg) as the atrium generates higher pressure to overcome the stenotic orifice 1
• Elevated mean left atrial pressure (often >15-20 mmHg in severe stenosis) is maintained throughout the cardiac cycle 1

Doppler Flow Patterns

• Prolonged mitral A wave duration with reduced peak velocity due to restricted flow through the narrowed orifice 1
• Increased E/A ratio may paradoxically occur in severe stenosis with elevated left atrial pressure, mimicking restrictive physiology 1
• Pressure half-time is prolonged (>220 ms in severe stenosis), reflecting slow deceleration of flow across the stenotic valve 1
• The A wave contribution to ventricular filling is disproportionately important, as early passive filling is severely restricted 3

Heart Sounds

• Loud S4 may be present if the patient is in sinus rhythm, reflecting forceful atrial contraction 1
• Opening snap occurs after S2, followed by a diastolic rumble that increases in intensity with atrial systole (presystolic accentuation) 1

Hemodynamic Impact

• Atrial systole contributes up to 40% of ventricular filling in mitral stenosis (versus 15-25% normally), making loss of atrial contraction (e.g., with onset of atrial fibrillation) particularly devastating 1, 3
• When atrial fibrillation supervenes in mitral stenosis, cardiac output may drop precipitously due to loss of this critical atrial contribution 1

Tricuspid Stenosis

Pressure Tracings

• Giant "a" wave in right atrial pressure and jugular venous pulse, often exceeding 15-20 mmHg in severe stenosis 1
• Slow y descent in the jugular venous pulse due to impaired right ventricular filling through the stenotic tricuspid valve 1
• Elevated mean right atrial pressure throughout the cardiac cycle, with a prominent pressure gradient during atrial systole 1

Doppler Flow Patterns

• Prolonged tricuspid A wave with reduced peak velocity, similar to mitral stenosis but on the right side 1
• Increased pressure half-time across the tricuspid valve (>190 ms suggests severe stenosis) 1

Clinical Correlation

• Tricuspid stenosis is almost always rheumatic and coexists with mitral stenosis in >90% of cases, so abnormalities of both valves appear simultaneously on the Wiggers diagram 1
• The presystolic murmur increases with inspiration (Carvallo's sign), distinguishing it from mitral stenosis 1

Key Diagnostic Pitfalls

• Do not confuse atrial fibrillation with complete AV block: In AF, the ventricular rhythm is irregularly irregular with no P waves; in complete AV block, the ventricular rhythm is regular with dissociated P waves 2
• Restrictive filling patterns in severe mitral stenosis can mimic restrictive cardiomyopathy on Doppler, but the presence of a stenotic valve orifice and elevated transmitral gradient distinguishes the two 1
• Cannon "a" waves in complete AV block occur randomly, whereas regular giant "a" waves in tricuspid stenosis occur with every atrial contraction 1, 2
• In atrial fibrillation with mitral stenosis, the loss of atrial systole eliminates the presystolic accentuation of the diastolic murmur and can precipitate acute decompensation 1