THE APEX CARDIOGRAM: ITS NORMAL FEATURES EXPLAINED BY THOSE FOUND IN HEART DISEASE

A Comparison of Heart Pulsations Provided by Forcecardiography and Double Integration of Seismocardiogram

Seismocardiography (SCG) is largely regarded as the state-of-the-art technique for continuous, long-term monitoring of cardiac mechanical activity in wearable applications. SCG signals are acquired via small, lightweight accelerometers fixed on the chest. They provide timings of important cardiac events, such as heart valves openings and closures, thus allowing the estimation of cardiac time intervals of clinical relevance. Forcecardiography (FCG) is a novel technique that records the cardiac-induced vibrations of the chest wall by means of specific force sensors, which proved capable of monitoring respiration, heart sounds and infrasonic cardiac vibrations, simultaneously from a single contact point on the chest. A specific infrasonic component captures the heart walls displacements and looks very similar to the Apexcardiogram. This low-frequency component is not visible in SCG recordings, nor it can be extracted by simple filtering. In this study, a feasible way to extract this information from SCG signals is presented. The proposed approach is based on double integration of SCG. Numerical double integration is usually very prone to large errors, therefore a specific numerical procedure was devised. This procedure yields a new displacement signal (DSCG) that features a low-frequency component (LF-DSCG) very similar to that of the FCG (LF-FCG). Experimental tests were carried out using an FCG sensor and an off-the-shelf accelerometer firmly attached to each other and placed onto the precordial region. Simultaneous recordings were acquired from both sensors, together with an electrocardiogram lead (used as a reference). Quantitative morphological comparison confirmed the high similarity between LF-FCG and LF-DSCG (normalized cross-correlation index >0.9). Statistical analyses suggested that LF-DSCG, although achieving a fair sensitivity in heartbeat detection (about 90%), has not a very high consistency within the cardiac cycle, leading to inaccuracies in inter-beat intervals estimation. Future experiments with high-performance accelerometers and improved processing methods are envisioned to investigate the potential enhancement of the accuracy and reliability of the proposed method.

Integrated Wearable Sensors for Sensing Physiological Pressure Signals and β-Hydroxybutyrate in Physiological Fluids

Flexible and wearable sensors have attracted much attention for their applications in health monitoring and the human-machine interaction. The most studied wearable sensors have been demonstrated for sensing a limited range of metabolites such as ions, glucose, uric acid, lactate, etc. Both sweat and urine contain numerous other physiologically relevant metabolites indicative of health and wellness. This work demonstrates the use of the wearable sensor for the detection of β-hydroxybutyrate (HB) in sweat. HB is an important biomarker for diabetic ketoacidosis, a condition caused by the accumulation of ketone bodies in hyperglycemia or metabolic acidosis patients. Herein, we fabricated an integrated sensing system coupling an HB detection chamber with a serpentine electrode for sensing physiological signals such as pulse beat, vocal cord vibration, etc. The real-time HB detection was based on a β-hydroxybutyrate dehydrogenase enzymatic reaction. The stability of the enzyme and the cofactor couple was achieved by cross-linking networks and a redox mediator, thereby achieving high selectivity and low detection limits to HB in urine and sweat. The dual-functional sensor was integrated with a signal processing circuitry for signal transduction, conditioning, processing, wireless transmission, and real-time convenient health monitoring display to a smartphone via home-developed software.

Stretchable E-Skin Apexcardiogram Sensor

A new strategy to measure the apex cardiogram with electronic skin technology is presented. An electronic skin apexcardiogram sensor, which can compensate the conventional electrocardiogram for cardiac diagnosis, is demonstrated through a highly sensitive and stretchable strain sensor with gold-nanoparticle composites.

Diastolic function in patients with coronary artery disease: effect of angina and heart failure functional class

The diastolic function of left and right parts of the heart using left and right mechanocardiogram method was investigated in 69 male patients with coronary artery disease and preceding myocardial infarction and in 18 normal patients. Nine patients were in angina class I, 28 were in class II, 32 were in class III. Forty-seven patients were in heart failure class II and 22 were in class III. The duration of isometric relaxation and atrium wave in left and right mechanocardiograms was more, and rapid filling wave was less in patients after myocardial infarction than in the control group. The duration of isometric relaxation and of atrium wave in left mechanocardiogram was more, and the duration of rapid filling wave was less in patients with heart failure class III than in patients in class II. The duration of isometric relaxation was more and the duration of rapid filling wave was less in right mechanocardiogram in patients with heart failure class III than in patients in class II. The diastolic abnormalities correlate more with the severity of heart failure than the angina severity. The diastolic abnormalities in right mechanocardiogram were found in patients without clinical manifestations of right ventricle failure.

Use of apexcardiography to evaluate left ventricular diastolic compliance in human beings

The relation between various relative amplitude measurements of the left apexcardiogram and internally derived indexes of diastolic compliance of the left ventricle was studied in 29 patients. Simultaneous high fidelity recordings of the left apex tracing and left ventricular pressure were obtained in 11 patients without left ventricular disease (group I) and 18 patients with congestive cardiomyopathy (group II). In 204 normal subjects the ratio of the A wave amplitude to the total diastolic deflection (A/D ratio) of the left apexcardiogram was 31.4 +/- 11.4 (mean +/- standard deviation) percent, the ratio of the A wave amplitude to the total height (A/H ratio) 8.9 +/- 4.3 percent and the D/H ratio 30.4 +/- 14.7 percent. The A/D and A/H ratios were significantly (P less than 0.001 and P less than 0.005) increased in group II (69.2 +/- 12.2 percent and 16.8 +/- 8.2 percent, respectively); they were within normal limits in group I. In contrast, the D/H ratio was within normal limits in both groups of patients. The A/D ratio correlated significantly better with specific compliance (deltaV/deltaP.V) (r = -0.87) than did the A/H ratio (r = -0.53), whereas similar correlations were obtained with end-diastolic volume compliance (dV/dPV) (r = -0.61 and r = - 0.64, respectively). In contrast, the D/H ratio correlated significantly only with end-diastolic distensibility index (dV/dP) (r = -0.52). It is concluded that A wave amplitude/total diastolic deflection (A/D) ratio and, to a lesser degree, the A wave amplitude/total height (A/H) ratio of the left apexcardiogram correspond best to diastolic compliance and are useful noninvasive measurements of this property of the left ventricle.

Slow filling period/rapid filling period ratio in the apexcardiogram: relation to the diagnosis of coronary artery disease

Apexcardiograms were performed in 68 consecutive patients who had either normal findings or coronary artery disease on cardiac catheterization. The height of the a wave in relation to the total apexcardiographic deflection (a/H) and the duration of both the rapid (RFW) and the slow (SFW) filling periods were determined in each case. The patients were classified into three gorups: I, no evidence of heart disease on catheterization; II, significant coronary artery disease with elevated left ventricular end-diastolic pressure; and III, coronary artery disease with normal filling pressure. There was a significant difference (P less than 0.001) between the SFW/RFW values (mean +/- 1 standard deviation) in control subject (group I, 2.3 +/- 0.5) and in subjects with coronary artery disease (group II, 4.7 +/- 1.6 and group III, 4 +/- 1.7). Setting the upper limit of normal for SFW/RFW at 2.8 (mean + 1 standard deviation) identified 94 percent of patients, in group II, 71 percent of patients in group III and 86 percent of all patients with coronary disease (group II plus group III). This sensitivity appeared greater than that of the a/H ratio. Only 2 of 17 patients (12 percent) without coronary atherosclerosis had an SFW/RFW ratio greater than 2.8. It is concluded that (1) the slow/rapid filling period ratio is a useful noninvasive measurement for identifying subjects with ischemic heart disease; (2) the increased values for slow/rapid filling period ratio associated with obstructive coronary lesions may be caused by impairment of early left ventricular distensibility; and (3) this ratio should be determined in patients with other forms of heart disease to determine its specificity.

Measurement of diastolic events by apexcardiogram: correlation with hemodynamic state and prognosis after myocardial infarction

Apexcardiograms and hemodynamic studies were performed in 32 postmyocardial infarction patients. Group 1 patients (5) had markedly elevated left ventricular end diastolic (LVED) pressures but normal LVED volumes; apexcardiograms included tall A waves (31 percent of the E to O points), prolonged A-wave durations of 134 msec or greater, short rapid filling wave durations (55 msec) and slow-filling waves replaced by plateaus in three patients. Group 2 patients (10) had markedly elevated LVED pressures and elevated LVED volumes, and had similar apexcardiographic findings: A-wave heights had a mean of 23.4 percent of E to O points, A-wave durations were 113 msec or more, rapid filling wave (RFW) durations were 93 msec and diastolic plateaus occurred in five patients. Group 3 patients (11) had intermediate hemodynamic findings and the apexcardiograms were varied; three patients with mild congestive heart failure (CHF) had apexcardiograms similar to Group 1 and five without CHF had apexcardiograms similar to those in Group 4. Group 4 patients (6) had normal hemodynamic findings; the mean A-wave height was 6 percent of the E to O point height, A-wave durations 90 msec or less RFW durations were 117.5 msec or more and the slow-filling wave duration (SFW) was normal in the configuration. Fourteen of 15 patients in Groups 1 and 2 developed CHF and six died on follow-up. Group 4 patients showed no evidence of CHF on follow-up and there were no deaths. Group differences were significantly different for A-wave height and duration, and for RFW duration at 0.05 or 0.01.Tall prolonged A waves and short RFWs were associated with poor left ventricular (LV) compliance and dysfunction, and diastolic plateau immediately following the RFW when present were confirmatory. Thus, the apexcardiogram is a reproducible useful noninvasive tool for clinical assessment, and predicting prognosis in postmyocardial infarction patients.

Diastolic intervals in cardiomyopathy and abnormal thyroid states: alterations in isovolumic relaxation time and rapid filling time of depressed and enhanced myocardial contractility

Diastolic and systolic time intervals were measured in 11 control subjects, 11 patients with cardiomyopathy, 7 hyperthyroid patients, and 5 hypothyroid patients. The isovolumic relaxation time (IVRT), rapid filling time (RFT), preejection period (PEP), left ventricular ejection time (LVET), and PEP/LVET ratio were found by simultaneously recording the ECG, phonocardiogram, external carotid pulse, and apexcardiogram. In cardiomyopathy the IVRT and RFT were prolonged (107.4 +/- 21.1 msec [P less than 0.01] and 111.0 +/- 10.0 [P less than 0.01] respectively) in comparison to the control subjects. (In the controls the IVRT was 85.7 +/- 18.4 msec and the RFT was 94.5 +/- 12.8 msec). In altered thyroid states the RFT was most affected; in hypothyroidism it increased to 123.9 +/- 25.2 (P less than 0.01) and in hyperthyroidism it decreased to 71.5 +/- 21.3 msec (P less than 0.01). In hyperthyroid patients the IVRT, although shorter than in control subjects, was not significantly altered, but it showed a significant increase after treatment. The RFT also returned toward normal after therapy in both groups (116.7 +/- 14.6 msec in hypothyroid patients and 89.0 +/- 23.1 msec in those with hyperthyroidism).

Magnet noncontact apexcardiography. A new technique for registering chest motion

A new apexcardiographic recording system has been developed which is free of certain technical limitations. This noncontact magnetic transducer was tested alternately with a commonly used pneumatic piezoelectric transducer in a comparative study on ten normal subjects. The magnetic registration offered a more accurate timing and configuration of the ACG. Signal distortion, such as peaked waves and an early fall of the systolic wave, was eliminated. The magnetic transducer was capable of recording directional apex point tracings, as well as pulsations of a larger apical area. The new system proved to possess definite advantages and eliminated some of the inconveniences inherent in the pneumatically coupled system.

Measurement of cardiac muscle relaxation in hypothyroidism

The isovolumetric relaxation time of the left ventricle (IRT) in 20 hypothyroid patients (133 +/- (SE of mean) 4 ms) was significantly longer than that in 23 normal subjects (95 +/- 3 ms). During a trial of thyroxine replacement the IRT in 12 hypothyroid patients fell from 143 +/- 4 ms to 107 +/- 4 ms. The IRT seems to be a useful index of end-organ function in hypothyroidism.

Relationship between duration of systolic upstroke of apexcardiogram and internal indexes of myocardial function in man

In 11 patients with nonobstructive cardiomyopathy and coronary heart disease and decreased myocardial function of the left ventricle, as well as in nine patients without left heart valvular or myocardial disease, left apexcardiograms were recorded during diagnostic heart catheterization, wherein micromanometers were used; ACG's were registered additionally in 54 healthy volunteers in order to establish the normal range of apexcardiographic parameters. In all cases the apex tracings were recorded by means of a pulse transducer with infinite time constant. The most important finding of this study was the close correlation between the duration of the systolic upstroke (SUT) of the apex tracing and some accepted isovolumic indexes of left heart function (isovolumic contraction time, time interval from the onset to peak of the first derivative of left ventricular pressure, maximal value of the first derivative of left ventricular pressure, and the peak measured velocity of shortening of the contractile elements). Further, the mean value of SUT in patients with impaired left myocardial function was significantly prolonged, compared to the control subjects; an overlap was apparent due to the fact that some of these patients showed a normal left myocardial performance at rest, having an abnormal response only to exercise tests. The apexcardiographic SUT can practically always be measured when the first derivative of apex tracing is simultaneously recorded. It showed itself to be only slightly influenced by the resting heart rate. The mentioned relationship of the systolic upstroke time of the ACG to internal isovolumic indexes of myocardial function makes this noninvasive measurable parameter an additional excellent tool for the evaluation of the left myocardial state, thus supporting a new aspect of the value of quantitative apexcardiography.

Diastolic time intervals in ischemic and hypertensive heart disease: A comparison of isovolumic relaxation time and rapid filling time with systolic time intervals

Isovolumic relaxation time (IVRT) and rapid filling time (RFT) were used to evaluate elasticity and compliance in 11 control subjects (Group 1), in nine patients with angina (Group 2), in 11 with hypertensive heasrt disease (Group 3), and in ten patients with healed myocardial infarction (Group 4). Pre-ejection period (PEP), pre-ejection period index (PEPI), left ventricular ejection time (LVET), left ventricular ejection time index(LVETI) and PEP/LVET ratio were all derived from simultaneous recordings of phonocardiograms, ECGs, apexcardiograms, and external carotid arterial pulses. No patients were in congestive heart failure and none were receiving medication. LVET and LVETI were the same in control patient groups; PEP was slightly increased in patients with healed myocardial infarctions (p smaller than 0.05); and PEPI was prolonged in the patients with angina (p = 0.001). THE PEP/LVET ratio too was different from the control group in patients with angina and hypertension (Groups 2 and 3-p smaller than 0.02 and smaller than 0.05 respectively). The diastolic time intervals were significantly altered in that the IVRT was prolonged in angina patients (113.4 equals or minus 28.3 msec), compared to control patients (85.7) equal or minus 18.4 msec). It was found that in 6 out of 9 patients with angina, this interval exceeded the highest normal value (108 msec), but that in only one out 11 patients with HCVD and in three out of ten with healed infarctions, was the interval prolonged. RFT was increased in HCVD (113.8 equals or minus 18.8 msec) and in healed myocardial infarction (123.8 equals or minus 30.0 msec) patients, compared to the control group (94.5 equals or minus 12.8 msec). Diastolic time intervals reflecting disorders in elasticity and compliance may occur in conjunction with alterations in systolic time intervals.

The A wave of the apexcardiogram and left ventricular diastolic stiffness

This study was made to determine whether the A wave of the apexcardiogram (ACG), a reflection of the late diastolic response of the left ventricle to atrial systole, corresponded in a quantifiable way to left ventricular late diastolic stiffness (LVDS). Using a combined ultrasonic and hemodynamic technique, the slope of the late diastolic left ventricular pressure/diameter relationship (ΔP/ΔD) was calculated in 25 patients and used as a measure of effective LVDS. Most patients had valvular heart disease, all were in sinus rhythm and none had regional abnormalities of contraction. An ACG was recorded in all and the ratio of the size of the A wave to the total amplitude of the ACG wave (A/H) was calculated. When A/H was more than 11%, left ventricular hypertrophy (LVH) and the presence of a fourth heart sound were the rule in the group of patients studied.

Using A/H as an independent variable, correlation coefficients were obtained for ΔP, ΔD, ΔP/ΔD, left ventricular end diastolic pressure (LVEDP), and left ventricular end diastolic volume (LVEDV). Correlation coefficients ( r ) were: ΔP = 0.68; ΔD = –0.05; ΔP/ΔD = 0.87; LVEDP = 0.73; LVEDV = 0.21. It is concluded that A/H corresponds best to LVDS and is a useful noninvasive measurement of this property of the left ventricle.

Phonocardiogram and apex cardiogram in systolic click--late systolic murmur syndrome

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Duration of phases of left ventricular systole using indirect methods. I. Normal subjects

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Third heart sound after mitral valve replacement

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The apexcardiogram in ischemic heart disease

The apexcardiogram (acg), when recorded serially in patients with acute myocardial infarction (ami), preinfarction angina (pia) and stable ischemic heart disease (ihd), appeared to reflect the abnormal patterns of contraction of the left ventricle in these conditions. Thus, paradoxical bulging (dyskinesis) of the systolic wave or increased "a" wave amplitude with gradual recovery over several weeks was found in all 60 patients with documented ami and in 18 of 20 patients with pia. Electrocardiogram changes were noted, however, in only eight of the pia patients. Changes in the acg frequently antedated ischemia in the ecg. Paradoxical bulging of the systolic wave of the acg was additionally noted in patients during the pain of angina pectoris but this promptly disappeared after the administration of nitroglycerine. Patients with classic angina often had normal resting ecg's but abnormal resting acg's. In contrast to the relatively transient abnormalities noted above, the acg remained unchanged in most patients with stable ihd during follow-up of three months to two years. Patients undergoing coronary bypass operations, however, showed immediate improvement in the acg in the postoperative period. These results suggest the acg reflects the contractile pattern of the left ventricle, and may be an indirectly recorded ventriculogram. Its enhanced sensitivity and the earlier development of changes in comparison to the ecg make this a valuable tool in the study of patients with heart disease.

Jugular, hepatic, and praecordial pulsations in constrictive pericarditis

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Isometric contraction period of the left ventricle in acute myocardial infarction

The usefulness of nontraumatic methods for measuring the left ventricular isometric contraction period (ICP) in myocardial infarction (MI) has been evaluated. The ICP was measured in 13 normal men and 38 patients admitted to a coronary care unit with chest pain, including 18 with acute MI, 12 with old MI, and nine with chest pain of miscellaneous origin; one of these nine was also included in the group with acute myocardial infarction. ICP was determined by three different methods: (1) time between the onset of systolic wave (A) of apexcardiogram (ACG) and the beginning of upstroke (C) of carotid pulse tracing (CPT); (2) time between A and ejection crest (E) of the ACG; and (3) time between the initial low frequency, low amplitude vibration of the first heart sound, and the C of CPT. Statistically significant differences of ICP between the normal group and the three groups of patients were demonstrated only by method 1. Likewise, acute coronary ligation in seven dogs produced characteristic changes in ICP by method 1, which were associated with a reduction in the left ventricular (LV) stroke volume, LV dp/dt, and the aortic flow velocity. The ICP obtained by method 1 appears to be of value in the bedside evaluation of acute myocardial infarction.

The apex cardiogram in left bundle-branch block

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The 'A' wave of the apex cardiogram in aortic valve disease and cardiomyopathy

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The apexcardiogram in myocardial asynergy

The apexcardiogram was analyzed in 41 patients with an altered pattern of left ventricular contraction. Four types were distinguished: type I, an early sustained systolic bulge which occurred in 12 patients, all of whom had large aneurysms and large enddiastolic volumes; type II, a bulge confined to midsystole which occurred in 13 patients, 11 of whom had some form of ventricular asynergy; type III, a late or end-systolic bulge which occurred in 12 patients, seven of whom had ventricular asynergy; type IV, a prominent spike during diastolic filling which occurred in four patients who had large zones of ventricular asynergy.

Evaluation of the contractile state of the human heart from the first derivative of the apexcardiogram

The first derivatives of the left ventricular pressure pulse (dp/dt LV) and of the apexcardiogram (Δ ACG) were recorded 73 times in 45 subjects, and the time intervals from the peak of the R wave of the electrocardiogram to the peak of the derivatives (t-dp/dt LV and t-Δ ACG) were determined under different circulatory conditions. These parameters express the duration of the development of maximum tension during isometric contraction of the ventricle. The values obtained from the left ventricular pressure pulse and from the ACG showed close correlation both at rest and after pharmacological interventions which enhanced or depressed the myocardial contractile state. During orciprenaline infusion, t-dp/dt LV and t-Δ ACG were consistently shortened, while they increased in most cases after beta-adrenergic receptor blockade.

Determination of the time to peak derivative of the ACG, a parameter so far unexplored, is proposed as a simple method of detecting changes in the myocardial contractile state in the intact human being.

Q-1 or C-1 interval in the diagnosis of mitral stenosis

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Normal cardiogram in the pulmonary area

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Quantitation of precordial movement. I. Normal subjects

A method has been devised for calibrating and measuring aspects of displacement records of cardiac movement. Forty-five normal subjects have been studied using this method, and a normal range has been calculated for the heights of the a wave, systolic outward movement, rapid-filling wave, and the ratio of rapid-filling wave to duration. The consistency of the results obtained and factors producing variations are discussed.

The A wave of the apex cardiogram in idiopathic hypertrophic subaortic stenosis

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