From the Guidelines
Cardiac reserve refers to the difference between the maximum cardiac output and the resting cardiac output, indicating the heart's ability to increase its output in response to physical activity or other stressors.
Key Components of Cardiac Reserve
- Heart Rate Reserve (HRR): the difference between the maximum heart rate and the resting heart rate, which is a key component of cardiac reserve 1.
- Stroke Volume Reserve: the ability of the heart to increase stroke volume in response to exercise or other stressors, which is also an important component of cardiac reserve 1.
Factors Affecting Cardiac Reserve
- Chronotropic Incompetence: the inability of the heart to increase its rate in response to exercise or other stressors, which can limit cardiac reserve 1.
- Left Ventricular Dysfunction: impaired left ventricular function can reduce cardiac reserve by limiting the heart's ability to increase its output in response to stressors 1.
- Pulmonary Hypertension: elevated pulmonary pressures can reduce cardiac reserve by increasing the afterload on the right ventricle and limiting its ability to increase its output 1.
Clinical Assessment of Cardiac Reserve
- Cardiopulmonary Exercise Testing (CPX): a non-invasive test that can be used to assess cardiac reserve and provide information on the heart's ability to respond to exercise 1.
- Heart Rate Reserve: can be calculated using the formula: HRR = maximum heart rate - resting heart rate, and can be used to estimate cardiac reserve 1.
From the Research
Definition of Cardiac Reserve
- Cardiac reserve refers to the difference between the heart's resting cardiac output and its maximum cardiac output during exercise or stress 2.
- It is a measure of the heart's ability to increase its output in response to increased demand, such as during physical activity 3.
Determinants of Cardiac Reserve
- Cardiac reserve is a major determinant of exercise capacity in patients with heart disease [(2,3)].
- It is influenced by factors such as cardiac power output, systolic and diastolic function, and chronotropic response [(4,5)].
- Sex differences can also impact the assessment of cardiac reserve, with differences in dose response to certain parameters 4.
Measurement of Cardiac Reserve
- Cardiac reserve can be measured non-invasively using techniques such as echocardiography and CO2 rebreathing 2.
- It can also be assessed using invasive hemodynamic measurements and Langendorff techniques 4.
- The choice of technique and parameters used can affect the accuracy of cardiac reserve measurements [(4,5)].
Clinical Significance of Cardiac Reserve
- Cardiac reserve is a prognostic tool for patients with heart failure, with lower reserves associated with poorer outcomes [(5,3)].
- It is also an important factor in determining exercise intolerance and aerobic capacity in patients with heart disease [(2,6)].
- Therapeutic interventions aimed at improving cardiac reserve can enhance exercise capacity and improve prognosis in patients with heart failure 3.