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A relative value method for measuring and evaluating cardiac reserve

Abstract

Background

Although a very close relationship between the amplitude of the first heart sound (S1) and the cardiac contractility have been proven by previous studies, the absolute value of S1 can not be applied for evaluating cardiac contractility. However, we w...

Methods

Tests were carried out on a varied group of volunteers. Four indicators were devised: (1) the increase of the amplitude of the first heart sound after accomplishing different exercise workloads, with respect to the amplitude of the first heart sound ...

Results

CCCT(1/4) was 6.36 ± 3.01 (n = 67), CCCT(1) was 10.36 ± 4.2 (n = 33), S1/S2 was1.89 ± 0.94 (n = 140), T1/M1 was 1.44 ± 0.99 (n = 144), and D/S was 1.68 ± 0.27 (n = 172).

Conclusions

Using indicators CCCT(1/4) and CCCT(1) may be beneficial for evaluating cardiac contractility and cardiac reserve mobilization level, S1/S2 for considering the factor for hypotension, T1/M1 for evaluating the right heart load, and D/S for evaluating ...

Keywords: Cardiac contractility, systolic diastolic duration, cardiac reserve, auscultation

Background

Total cardiac reserve involves heart rate reserve, diastole volume reserve, systole volume reserve, coronary reserve [1], metabolic reserve [2], plasma norepinephrine reserve [3], etc. The measurement and evaluation of cardiac reserve is an important...

Previous studies of cardiac reserve mainly involved chronotropic incompetence, fewer involved inotropic incompetence [3-5]. It is a generally accepted concept that exercise capacity is a more powerful predictor of mortality than other established ris...

However, the distance covered during a 6-min walk test does not just represent cardiac reserve. Previous studies on the relationship between the amplitude of the first heart sound (S1) and cardiac contractility offer a way to reconcile the measuremen...

Based on the close relationship between the amplitude of the first heart sound (S1) and the cardiac contractility, we also devised another two indicators to evaluate specific cardiovascular status. One was the ratio of the amplitude of the first hear...

Furthermore, the time in diastole, when myocardial blood perfusion occurs, is an indicator of cardiac reserve. Whether or not this time during diastole is sufficient relates to how much nutrition and oxygen will be available during systole. This avai...

The primary objective of this work was to devise some indicators based on relative values for evaluating cardiac function, since the absolute value of S1 can not be used for evaluating cardiac contractility. We used the indicators described above to ...

Methods

Subjects

One hundred and seventy-two volunteer subjects aged 15Ð82 (83 males and 89 females) were included in this study, and underwent different measurements on a voluntary basis. These subjects consisted of 20 with hypertension, 4 with grade III to VI systo...

The study was approved by the Review Committee of Chongqing University and informed consent was given by every subject.

Instrumentation

An Exercise Cardiac Contractility Monitor (ECCM, developed by Bo-Jing Medical Informatics Institute, Chongqing, China) was used for this investigation. The hardware of ECCM consists of a phonocardiographic sensor, a heart sound signal preprocessing b...

Basic points of design

The basic points for heart sound quantitative analysis were: (1) measuring the duration and the amplitude of relevant heart sound components;(2) generating relevant indicators based on the data obtained from the measurements. As the chest thicknesses...

Exercise testing

The phonocardiogram exercise test (PCGET) [15-17] was used for this investigation. Examination was started after the subject entered the test room and rested for 15 min. A PCG sensor was placed on the subject's pericardium. Phonocardiograms were reco...

All measurements and analyses were performed in a common office.

Calculation and Statistical analysis of measurement data

The increase of the amplitude of the first heart sound after completing one-fourth of the whole exercise workload, with respect to the amplitude of the first heart sound recorded at rest was designated as CCCT(1/4); the increase of the amplitude of t...

Results

The data of CCCT(1/4), CCCT(1), S1/S2, T1/M1, and D/S were approximately a normal distribution, as shown in Table 1 below.

Table 1

The statistics of CCCT(1/4), CCCT(1), S1/S2, T1/M1, and D/S

* p < 0.01; N: number of subjects; CCCT = cardiac contractility change trend; CCCT(1) = CCCT for completing the whole workload (7000 J); CCCT(1/4) = CCCT for completing one-fourth of the whole workload (1750 J); S1/S2 = the ratio of the amplitude of ...

The cutoff point of D/S was selected and evaluated from multiple aspects, including receiver operator characteristic curve (ROC curve) and likelihood ratio, which was 1.5. At the one-year follow up, total death rate of subjects with D/S < 1.5 was 9 %...

Discussion

There are many methods for measuring and evaluating cardiac function. For example, electrocardiogram examination is the optimal method for monitoring myocardial chronotropism and dromotropism. However, it is unable to be used to monitor inotropism. C...

Until now, the New York Heart Association's Functional Classification (NYHA FC) is still used very widely. Attempts at improvement of NYHA FC by overcoming its subjectivity continue; for example the revision of the 1995 Guidelines for the Evaluation ...

Table 1 shows that there is a very significant difference between CCCT(1/4) and CCCT(1) (p < 0.01), which suggests that using indicators CCCT(1/4) and CCCT(1) may be beneficial for evaluating cardiac contractility and cardiac reserve mobilization lev...

There are many factors that can interfere with the intensity of the first heart sound, such as respiration, exercise, psychological activity, drugs, temperature, smoking, disease, etc. Therefore, performing this kind of examination should follow a un...

Because the limited number of disease types and corresponding patient examples, we did not perform stratified statistics. But we compared the difference of T1/M1 between 144 subjects without pulmonary heart disease from the group in this study with 3...