Why does right ventricular (RV) failure cause low diastolic blood pressure?

Why Right Ventricular Failure Causes Low Diastolic Blood Pressure

Right ventricular failure causes low diastolic blood pressure primarily through reduced left ventricular filling, resulting from decreased forward flow through the pulmonary circulation and ventricular interdependence mechanisms. 1

Pathophysiological Mechanisms

1. Reduced Forward Flow

• When the right ventricle (RV) fails, it cannot maintain adequate cardiac output through the pulmonary circulation
• This leads to decreased pulmonary venous return to the left heart
• Consequently, left ventricular (LV) filling is reduced, resulting in decreased stroke volume and lower systemic blood pressure, particularly affecting diastolic pressure 1

2. Ventricular Interdependence

• The RV and LV share the interventricular septum and are contained within the pericardial space
• In RV failure, RV dilation causes:
  • Leftward shift of the interventricular septum
  • Mechanical compression of the LV cavity
  • Impaired LV filling during diastole 1
• This ventricular interdependence is particularly pronounced with an intact pericardium, as RV dilation compresses the LV cavity and impedes LV filling 1

3. Altered Coronary Perfusion

• Unlike the LV, which receives coronary flow predominantly during diastole, the RV normally receives coronary perfusion during both systole and diastole
• In RV failure, decreased systemic arterial pressure (particularly diastolic) reduces coronary perfusion pressure
• This creates a vicious cycle where RV ischemia worsens RV function, further decreasing cardiac output 1

4. Ventriculo-arterial Uncoupling

• RV failure disrupts the normal coupling between RV contractility (end-systolic elastance) and afterload (arterial elastance)
• This uncoupling makes RV function inefficient, requiring more energy expenditure to maintain output
• The result is further deterioration of RV function and systemic perfusion 1

Clinical Manifestations and Hemodynamic Consequences

Acute RV Failure

• Abrupt decrease in RV stroke volume with minimal increase in RV systolic pressure
• Steep decline in stroke volume compared to the LV's response to similar pressure increases 1
• Reduced systemic cardiac output leading to hypotension, with diastolic pressure particularly affected

Chronic RV Failure

• Progressive RV dilation with tricuspid regurgitation
• Biventricular diastolic dysfunction with equalization of diastolic pressures
• Reduced cardiac output with peripheral and abdominal congestion 1
• Systemic hypoperfusion manifesting as low diastolic pressure

Clinical Implications

• Low diastolic pressure in RV failure creates a dangerous cycle where coronary perfusion is compromised, potentially worsening myocardial function
• Vasopressors like norepinephrine may be necessary in cardiogenic shock to improve systemic hemodynamics and coronary perfusion 1
• Cautious volume management is critical, as excessive volume loading can worsen RV distention and further compromise LV filling 1
• Monitoring for signs of elevated central venous pressure is essential to guide fluid management in RV failure 1

Management Considerations

• Treatment should focus on optimizing RV preload, reducing RV afterload, and supporting RV contractility
• Maintaining adequate systemic blood pressure is crucial for RV perfusion
• Systemic systolic arterial pressure should be kept close to RV systolic pressure to maintain RV coronary perfusion 2
• Selective pulmonary vasodilators may help reduce RV afterload without worsening systemic hypotension 2

In summary, RV failure leads to low diastolic blood pressure through reduced forward flow, ventricular interdependence mechanisms, and a cycle of worsening RV function that compromises systemic perfusion. This hemodynamic consequence has important implications for coronary perfusion and requires careful management to avoid further deterioration.