From the Guidelines
Afterload is the resistance that the heart must overcome to eject blood during contraction, representing the force against which the ventricles must pump to push blood into the circulation.
Definition and Determinants of Afterload
Afterload is a critical determinant of cardiac performance and is primarily determined by systemic vascular resistance and arterial blood pressure in the left ventricle, while in the right ventricle, it's determined by pulmonary vascular resistance. According to 1, afterload is most appropriately defined as the RV wall stress during systolic ejection estimated by the summation of the resistive and pulsatile components of blood flow.
Clinical Implications of Afterload
Increased afterload makes the heart work harder, requiring more oxygen and energy to maintain adequate cardiac output. This can lead to cardiac hypertrophy over time as the heart muscle thickens to generate more force. Conditions that increase afterload include hypertension, aortic stenosis, and peripheral vascular disease. As noted in 1, hypertension is a risk factor for AS and associated with increased rate of progression and reduced survival, highlighting the importance of managing afterload in clinical practice.
Management of Afterload
Medications that reduce afterload, such as vasodilators (e.g., ACE inhibitors, angiotensin receptor blockers, and calcium channel blockers), are commonly used to treat heart failure and hypertension by decreasing the workload on the heart. Understanding afterload is crucial for managing cardiovascular diseases as it directly affects cardiac performance and efficiency. As discussed in 1, the choice of surgical versus transcatheter AVR for patients with an indication for AVR is critical in managing afterload and improving patient outcomes.
Key Points
- Afterload is the resistance that the heart must overcome to eject blood during contraction.
- Increased afterload can lead to cardiac hypertrophy and decreased cardiac performance.
- Conditions that increase afterload include hypertension, aortic stenosis, and peripheral vascular disease.
- Medications that reduce afterload, such as vasodilators, are commonly used to treat heart failure and hypertension.
- Understanding afterload is crucial for managing cardiovascular diseases and improving patient outcomes, as highlighted in 1 and 1.
From the FDA Drug Label
Amlodipine reduces the total peripheral resistance (afterload) against which the heart works and reduces the rate pressure product, and thus myocardial oxygen demand, at any given level of exercise Nitroglycerin also produces arteriolar relaxation, thereby reducing peripheral vascular resistance and arterial pressure (afterload)
Afterload is the resistance that the heart must overcome to eject blood into the systemic circulation. It is the pressure against which the heart works to pump blood. In other words, afterload is the peripheral vascular resistance or the pressure in the arteries that the heart must pump against to deliver blood to the body.
- Key points:
From the Research
Definition of Afterload
- Afterload is defined as all of the factors that contribute to total myocardial wall stress (or tension) during systolic ejection 4.
- It can also be described as the resistance that the ventricles must overcome to eject blood into the peripheral circulation 5.
- Afterload is an important concept in cardiac physiology, as it affects the performance of the heart and can be influenced by various factors, including systemic vascular resistance, blood pressure, and cardiac function.
Factors that Contribute to Afterload
- Systemic vascular resistance (SVR) is a key factor that contributes to afterload, but it is not a reliable index of left ventricular afterload, as it only reflects peripheral vasomotor tone 6.
- Left ventricular end-systolic wall stress (sigma es) is a more accurate measure of afterload, as it reflects the combined effects of peripheral loading conditions and left ventricular chamber pressure, dimension, and wall thickness 6.
- Other factors that can influence afterload include blood pressure, cardiac output, and vascular compliance.
Clinical Significance of Afterload
- Afterload is an important predictor of mortality in patients with chronic heart failure, and afterload-related cardiac performance (ACP) is a powerful independent hemodynamic predictor of mortality in these patients 7.
- An increase in afterload can unmask systolic abnormalities in heart failure with preserved ejection fraction (HFpEF), and provocative maneuvers such as an afterload challenge can be used to detect preclinical and early-stage HFpEF 8.
- Afterload reduction is a key therapeutic strategy in the treatment of congestive heart failure, and systemic vasodilators can be used to decrease afterload and improve cardiac performance 5.