From the Guidelines
Preload cardiac refers to the amount of blood that fills the ventricles of the heart at the end of diastole, representing the stretching of cardiac muscle fibers prior to contraction and a key determinant of cardiac output. This concept is crucial in managing patients with cardiovascular disease, particularly in conditions like heart failure where excessive preload can worsen symptoms. According to the Frank-Starling mechanism, an increase in preload causes greater stretching of cardiac muscle fibers, resulting in stronger contractions and increased stroke volume up to a physiological limit 1.
Key Points About Preload
- Preload is primarily determined by venous return to the heart and can be clinically estimated by measuring central venous pressure or pulmonary capillary wedge pressure.
- Clinicians manipulate preload in various clinical scenarios, such as increasing it with intravenous fluids in hypovolemic states or decreasing it with diuretics like furosemide or nitroglycerin in conditions like heart failure.
- Understanding preload is essential for managing hemodynamics in critical care settings and optimizing cardiac function in patients with cardiovascular disease.
Clinical Management
In clinical practice, the management of preload is critical, especially in patients with heart failure. Decreasing preload with diuretics like furosemide (20-40mg IV) or nitroglycerin (starting at 5-10 mcg/min IV) can help alleviate symptoms of heart failure. However, it's also important to avoid preload depletion, which can lead to decreased cardiac output, as noted in patients with Fontan circulation who require careful management of fluid overload 1.
Recent Guidelines and Recommendations
Recent studies and guidelines emphasize the importance of careful preload management. For instance, the use of nitroglycerin in acute cardiogenic pulmonary edema is recommended to optimize preload and decrease afterload 1. Additionally, considerations for advanced heart failure consultation in individuals with Fontan circulation highlight the need for careful management of symptomatic fluid overload to prevent preload depletion and decreased cardiac output 1.
Conclusion Not Applicable - Direct Answer Only
The most recent and highest quality study 1 supports the importance of managing preload in heart failure patients, emphasizing the need for a balanced approach to avoid both excessive preload and preload depletion.
From the FDA Drug Label
Dilation of postcapillary vessels, including large veins, promotes peripheral pooling of blood, decreases venous return to the heart, and reduces left ventricular end-diastolic pressure (preload)
Preload cardiac refers to the initial stretching of the cardiac myocytes prior to contraction, which is related to the left ventricular end-diastolic pressure. It is the volume of blood in the ventricles at the end of diastole, and is a key determinant of cardiac output. In the context of the provided drug label, nitroglycerin reduces preload by decreasing venous return to the heart, thereby reducing left ventricular end-diastolic pressure 2.
- Key points:
- Preload is the initial stretching of cardiac myocytes
- Related to left ventricular end-diastolic pressure
- Nitroglycerin reduces preload by decreasing venous return
- Resulting in reduced left ventricular end-diastolic pressure
From the Research
Definition of Preload Cardiac
- Preload cardiac refers to the initial stretching of the cardiac myocytes prior to contraction, which is directly related to the volume of blood in the ventricles at the end of diastole [(3,4,5,6,7)].
- It is an important determinant of cardiac output, as increased preload can lead to increased stroke volume according to the Frank-Starling law [(3,4,5,6,7)].
Factors Affecting Preload
- Preload is affected by factors such as venous return, ventricular compliance, and atrial contraction [(3,4,5,6,7)].
- Vasodilators, such as nitroglycerin and nitroprusside, can decrease preload by reducing venous return [(3,4,7)].
- Diuretics, such as furosemide, can also decrease preload by reducing fluid volume [(4,5,6)].
Clinical Significance
- Understanding preload is crucial in the management of heart failure, as it can help guide treatment decisions [(3,4,5,6,7)].
- Monitoring preload can help clinicians assess the effectiveness of treatments and make adjustments as needed [(3,4,5,6,7)].