NICaS Heart Failure Event Monitoring, UK
Physiology of HF:
When a patient's heart begins to fail, it can no longer pump a sufficient amount of blood to meet the body's metabolic demands. Cardiac output is the amount of blood pumped by the left ventricle into the aorta each minute. In a heart failure patient, the cardiac output will be lower than normal. As shown in Figure 1 below, cardiac output is determined by two parameters - heart rate and stroke volume. Stroke volume is determined by three parameters - preload, afterload, and contractility.
Figure 1. Determinants of Cardiac Output and medications that affect these determinants. 1
Although there will be variability from patient to patient and even within the same patient over time, a typical "hemodynamic profile" of a patient with an exacerbation of heart failure is shown in Figure 1. The cardiac output will be decreased due to the heart rate being either increased or decreased, but stroke volume, the amount of blood pumped by the left ventricle each beat, will be decreased. Preload, the amount of blood available for the left ventricle to pump, will often be increased. Afterload, the systemic vascular resistance to the flow of blood, will often be increased. Contractility, the speed and strength of the left ventricle, will often be decreased.
Objective data can lead to better outcomes and decreased cost of care.
NICaSTM provides data that directly or indirectly relate to cardiac output and each of its determinants. When physicians have access to these objective data, they can make more accurate diagnoses,2 utilize these data to guide therapy,3 achieve better outcomes,3 decrease cost of care,4 and identify heart failure patients at high risk of hospital readmission5,6.
Figure 2 below illustrates the additional clinical power provided by NICaSTM. The standard parameters of height, weight, blood pressure, and heart rate are shown in the box in the upper left. The NICaSTM Status Report, shown on the right half of the illustration, provides these standard parameters, plus the additional parameters of Stroke Volume, Stroke Index, Cardiac Output, Cardiac Index, Total Peripheral Resistance, Total Body Water, Respiration Rate, Granov-Goor Index, and Cardiac Power Index. The values of these parameters are plotted versus low, normal and high norms, so that the healthcare provider can instantly recognize which values are outside of their normal range. Additionally, the user can select three parameters to be plotted versus time, so that the healthcare provider can see trends in these parameters.
Figure 2. Sample NICaSTM Status Report from a patient with heart failure.
Predictive power of NICaSTM Parameters:
As heart failure worsens, these patients will experience episodes of "decompensation" (acute worsening of the heart's inability to pump blood), which not only adversely affects the quality of the patient's lifestyle and may be fatal, but also, significantly increases the cost of caring for these patients, due primarily to hospitalization costs. Consequently, it would be beneficial to be able to identify heart failure patients at high risk of hospital readmission and focus resources on them to try to improve their condition and prevent hospital readmission.5
Tanino and associates published results of a study designed to determine which parameters would identify heart failure patients at risk of hospital readmission.6 Sixty-eight heart failure patients were enrolled upon discharge from a hospital and followed for an average of 100 days. During the follow-up period, there were 15 readmissions due to heart failure. The parameters that were predictive of hospital readmission due to exacerbation of heart failure are shown below in Figure 3.
Figure 3. Parameters predicting hospital readmission in heart failure patients.6
The predictive parameters were: BNP = B-type Naturetic Peptide, NICaSTM derived Cardiac Index, Stroke Index, and Systemic Vascular Resistance, Left Ventricular Ejection Fraction, and Exercise Tolerance. Of the six parameters identified as being predictive of hospital readmissions, three were from NICaSTM: Cardiac Index < 2.49, Stroke Index < 27.2, and Systemic Vascular Resistance > 2597. Since BNP required a blood sample, LVEF required an ultrasound measurement, and Exercise Tolerance required an exercise test, NICaSTM provided a simpler, more cost effective way to obtain parameters that predicted readmission of the heart failure patients in this study.6
Related Clinical Studies:
- Adapted from Yancy, C, Abraham W. Congest Heart Fail 2003; 9(5): 241-250. and AHA Practice Guidelines http://www.acc.org/ 2005:1-82
- Springfield, CL, et al., CHF; 10(2 suppl2):14-16. Smith, RD, et al., Hypertension. 2006; 47:769-775.
- Ferrario, CM, et al., Am Heart Hosp J. 2006; 4:279-289.
- Packer, M, et al., J Am Coll Cardiol 2006; 47:2245-52.
- Tanino, Y et al., Circulation Journal2009; 73: 1074 - 1079