Normal RV Function and Pulmonary Circulation
Healthy RV pumps low-pressure, low-resistance flow to the lungs.
- 1x: Normal PVR (baseline reference)
- ~3-5mm: RV wall thickness (thin, compliant)
- 100%: Normal CO (resting baseline)
- ~90-118: Mean systemic BP (mmHg, stable)
RV as a low-pressure pump
Thin-walled RV suited to a low-resistance pulmonary circuit.
Septal geometry at rest
Septum curves toward RV; LV filling is unimpeded.
Acute Pulmonary Arterial Obstruction
A large embolus lodges, blocking a major share of pulmonary flow.
- >50%: Clot burden (flow blocked, massive PE)
- Sudden: Onset (minutes)
- DVT: Source (proximal leg veins, typical)
- Large: Territory affected (main/lobar arteries)
Where clots lodge
Large emboli wedge at main or lobar pulmonary artery bifurcations.
Immediate mechanical effect
Flow is diverted, cross-sectional area for perfusion drops sharply.
Pulmonary Vascular Resistance and Acute RV Afterload
Obstruction plus reflex vasoconstriction sharply raises PVR.
- Up to 5x: PVR rise (relative to baseline)
- Acute ↑: RV afterload (sudden pressure load)
- Hypoxia, serotonin: Mediators (vasoconstrictors released)
- Minutes: Time course (rapid onset)
Mechanical + humoral resistance rise
Physical obstruction compounds with vasoactive mediator release.
RV pressure-work spikes
Unprepared thin RV faces a sudden, steep pressure load.
RV Dilation, Wall Tension, and Septal Bowing
The RV dilates, wall tension rises, septum bows into the LV.
- Marked: RV size increase (acute dilation)
- Leftward: Septal shift (bows into LV cavity)
- Reduced: LV filling (via septal compression)
- High: Wall tension (Laplace relationship)
Dilation and wall stress
Rising volume and pressure raise RV wall tension acutely.
Ventricular interdependence
Bowing septum crowds LV, limiting its diastolic filling.
Falling Output and Obstructive Shock
Cardiac output and BP fall; shock develops without urgent care.
- ↓↓: Cardiac output (markedly reduced)
- <90 mmHg: Systemic BP (hypotension threshold)
- Obstructive: Shock type (mechanical outflow block)
- Immediate: Urgency (thrombolysis/embolectomy)
Output collapse mechanism
Reduced LV preload plus failing RV output drop systemic flow.
Urgent reperfusion therapy
Thrombolysis, embolectomy, or anticoagulation reverse the cascade.
Rapid reperfusion can reverse RV strain before arrest.