From the Guidelines
Aortic stenosis does increase afterload.
Pathophysiology of Aortic Stenosis
The increased resistance to left ventricular (LV) ejection with aortic stenosis (AS) causes increased LV afterload, as the physical obstruction to LV ejection requires increased pressure to be developed to propel blood across the reduced aortic orifice 1.
- The increased stiffness of the aortic valve and reduced orifice area result in a higher than normal resistance to ejection, leading to increased LV pressure throughout the ejection phase 1.
- This increased afterload can lead to LV hypertrophy (LVH) as the left ventricle adapts to the systolic pressure overload through a hypertrophic process, resulting in increased LV wall thickness while maintaining a normal chamber volume 1.
- However, if the hypertrophic process is inadequate, wall stress increases, and the high afterload causes a decrease in ejection fraction 1.
Clinical Implications
The development of concentric hypertrophy appears to be an appropriate and beneficial adaptation to compensate for high intracavitary pressures, but it often carries adverse consequences, such as reduced coronary blood flow per gram of muscle and increased sensitivity to ischemic injury 1.
- Treatment of hypertension is a valid target in patients with AS, as it increases LV afterload and thereby LV mass, which is independently associated with mortality 1.
- The European Society of Cardiology (ESC) and American Heart Association/American College of Cardiology (AHA/ACC) guidelines recommend treatment of hypertension in patients with AS, with pragmatic goals of a systolic blood pressure of 130–139 mmHg and a diastolic blood pressure of 70–90 mmHg 1.
From the Research
Aortic Stenosis and Afterload
- Aortic stenosis is characterized by an increased afterload, which can lead to compensatory concentric hypertrophy and mitigate the increased systolic load 2.
- The increased afterload in aortic stenosis is due to both the stenotic aortic valve and the peripheral vascular resistance (PVR) 3.
- Valvulo-arterial impedance (ZVa) is a parameter that permits the evaluation of global left ventricular afterload in aortic stenosis, and an increase in ZVa is associated with a progressive reduction in global longitudinal and circumferential left ventricular strain 3.
Effects of Aortic Stenosis on Left Ventricular Function
- Aortic stenosis can lead to left ventricular remodeling, which is a complex multidetermined process that goes beyond myocardial hypertrophy 4.
- The left ventricular adaptation to increased afterload in aortic stenosis is not uniform and can involve ultrastructural changes, including diffuse and replacement fibrosis of the myocardium 4.
- The presence of inappropriately decreased stroke volume relative to afterload in patients with severe aortic stenosis and normal left ventricular ejection fraction is associated with lower contractility, higher heart rate, shorter ejection time, and elevated left ventricular diastolic pressure 5.
Afterload Reduction and Left Ventricular Function
- Afterload reduction, such as that achieved through transcatheter aortic valve intervention (TAVI), can lead to left ventricular remodeling and a decrease in afterload 2.
- However, the response to afterload reduction is complex, and systolic function may not improve despite a decrease in afterload 2.
- The evaluation of left ventricular function and afterload should be comprehensive, especially in cases of diagnostic challenge, as disregarding their effects may lead to an underestimation of stenosis severity and a potential delay in therapeutic intervention 6.