Changes in systemic vascular resistance detected by the arterial resistometer: preliminary report of a new method tested during percutaneous transluminal coronary angioplasty

Studying the correlations among hematological and serum biochemical constituents in cattle theileriosis

The present study was undertaken to investigate the influence of tropical theileriosis on serum constituents, erythrocytes and platelets pictures and to study the correlation between the studied parameters. A total number of 26 cows were subjected to study. Out of them 16 cows were suffered from theileria infection. Comparing theileria infected group with the control group revealed significant decreases in total RBCS counts (p < 0.01), haemoglobin concentration (p < 0.01), packed cell volume (PCV) (p < 0.01), platelets count (PLT) (p < 0.01), plateletcrit (PCT) (p < 0.01), significant decreases in serum total proteins (p < 0.01), albumin (p < 0.01), calcium (p < 0.01), and phosphorus (p < 0.01) levels, and significant increases in serum blood urea nitrogen (BUN) (p < 0.05) and creatinine (p < 0.05) levels, and in serum aspartate aminotransferase (p < 0.01) and gamma glutamyl transferase (GGT) (p < 0.01) activities. Correlations between serum biochemical parameters revealed significant positive correlations between total proteins and albumin (r = 0.598*), A/G ratio and albumin (r = 0.860**), calcium and albumin (r = 0.729*), calcium and A/G ratio (r = 0.752*), GGT and BUN (r = 0.539*), and significant negative correlations between A/G ratio and globulins (r = -0.809**) and between glucose and albumin (r = -0.614*). Erythrocytes count showed a significant negative correlation with mean corpuscular volume (MCV) (r = -0.966**) and red blood cells distribution width (RDW) (r = -0.909**). MCV showed a significant positive correlation with RDW (r = 0.860*) and PCV (r = 0.781*). RDW was positively correlated with PCV (r = 0.966**). PLT count showed a significant positive correlation with mean platelet volume (MPV) (r = 0.992**), platelets distribution width (PDW) (r = 0.956**) and PCT (r = 0.994**). Furthermore, MPV showed a significant positive correlation with PDW (r = 0.940**) and a negative correlation with PCT (r = -0.974**). PDW was negatively correlated with PCT (r = -0.974**). It could be concluded that theileria infection in cattle resulted in anaemia, thrombocytopenia, hypoproteinaemia, hypoalbuminaemia and hypophosphataemia, in addition to hepatic and kidney dysfunction.

A new noninvasive device for measuring central ejection dP/dt mathematical foundation of cardiac dP/dt measurement using a model for a collapsible artery

We have developed a novel non-invasive device for the measurement of one of the most sensitive indices of myocardial contractility as represented by the rate of increase of intraventricular pressure (left ventricular dP/dt and arterial dP/dt performance index (dP/dt(ejc)). Up till now, these parameters could be obtained only by invasive catheterization methods. The new technique is based on the concept of applying multiple successive occlusive pressures on the brachial artery from peak systole to diastole using a inflatable cuff and plotting the values against time intervals that leads to the reconstruction of the central aortic pressure noninvasively. The following describes the computer simulator developed for providing a mathematical foundation of the new sensor. At the core of the simulator lies a hemodynamic model of the blood flow on an artery under externally applied pressure. The purpose of the model is to reproduce the experimental results obtained in studies on patients (Gorenberg et al. in Cardiovasc Eng: 305-311, 2004; Gorenberg et al. in Emerg med J 22 (7): 486-489, 2005) and a animal model where ischemia resulted from balloon inflation during coronary catheterization (Gorenberg and Marmor in J Med Eng Technol, 2006) and to describe correlations between the dP/dt(ejc) and other hemodynamic variables. The model has successfully reproduced the trends observed experimentally, providing a solid in-depth understanding of the hemodynamics involved in the new measurement. A high correlation between the dP/dt(ejc) and the rate of pressure rise in the aorta during the ejection phase was observed. dP/dt(ejc) dependence on other hemodynamic parameters was also investigated.

Validation of a novel method to determine non-invasively the rate of central aortic pressure changes

INTRODUCTION

One of the most sensitive indices of myocardial contractility is represented by the rate of increase of intraventricular pressure during isovolumetric contraction (dP/dt) and (dP/dt(ejc)), which represents the rate of change of pressure during ejection. Today these parameters can be obtained only by invasive catheterization methods. We developed a novel technique that leads to the non-invasive reconstruction of the central aortic pressure. The technique is based on the concept of applying multiple successive occlusive pressures on the brachial artery from peak systole to diastole using an inflatable cuff and plotting the values against time intervals. The hypothesis is that the time intervals required for the aortic pressure wave to overcome a given occlusive brachial pressure applied by a sphyngomanometer on the arm are equal to time needed to reach the same pressure in the central aorta plus the propagation time to the brachial point, which is constant in the same patient throughout the measurements.

METHODS AND RESULTS

We tested the hypothesis using an animal experiment. The new non-invasive device was mounted on the left forelimb of the animal. A Millar pressure transducer catheter was inserted to the aorta and the aorta pressure was recorded at time intervals of 1 ms. A second catheter was inserted into the coronary arteries and used to create controlled occlusion of the arteries using a balloon inflated to 10 atm. Measurements were obtained before the intervention was started, and throughout the sequence of repeated occlusions and deflations. At the end of the sequence, IV dobutamine was administered and results were monitored for 10 min while the heart rate and blood pressure were rising. Non-invasive dP/dt(ejc) was reduced typically by 20% in response to balloon inflation. In long occlusion periods, stabilization and sometimes recovery of dP/dt(ejc) is observed. By plotting dP/dt(ejc) measured by the new non-invasive device versus catheter measurements a correlation factor of 0.843 was found.

CONCLUSION

A newly developed method of non-invasive measurement of central dP/dt has been found to correlate to invasive measurements in an animal model.

Acute coronary syndromes in the emergency department: diagnostic characteristics, tests, and challenges

Failure to diagnose patients who have acute coronary syndromes (ACSs)-either acute myocardial infarction (AMI) or unstable angina pectoris (UAP)-who present to the emergency department (ED) remains a serious public health issue. Better understanding of the pathophysiology of coronary artery disease has allowed the adoption of a unifying hypothesis for the cause of ACSs: the conversion of a stable atherosclerotic lesion to a plaque rupture with thrombosis. Thus, physicians have come to appreciate UAP and AMI as parts of a continuum of ACSs. This article reviews the state of the art regarding the diagnosis of ACSs in the emergency setting and suggests reasons why missed diagnosis continues to occur, albeit infrequently.

Non-invasive measurement of cardiac output by whole-body bio-impedance during dobutamine stress echocardiography: Clinical implications in patients with left ventricular dysfunction and ischaemia

OBJECTIVES

To compare non-invasive determination of cardiac index (CI) by whole body electrical bioimpedance using the NICaS apparatus and Doppler echocardiography, and the role of cardiac power index (Cpi) and total peripheral resistance index (TPRi) calculation during dobutamine stress echocardiography (DSE).

SUBJECTS AND METHODS

We enrolled 60 consecutive patients undergoing DSE. Patients were prospectively divided into 3 groups: Group 1 (n = 20): normal DSE (control). Group 2 (n = 20): EF<40% without significant ischaemia. Group 3 (n = 20): patients with significant ischaemia on DSE. Measurements of CI were performed at the end of each stage of DSE by both echocardiographic left ventricular outflow track flow and the NICaS apparatus, using whole-body bio-impedance. MAP was measured simultaneously and TPRi and Cpi were calculated.

RESULTS

The correlation between non-invasive CI as determined by NICaS and echocardiography was 0.81, although Echocardiographic readings of CI were higher during administration of higher doses of dobutamine. Lower EF correlated with lower Cpi, especially stress induced Cpi. Hence, patients with reduced EF (group 2) had a blunted increase in Cpi during stress. Patients with ischaemia (group 3) had a blunted increase in Cpi as well as a decrease in Cpi and increase in TPRi during the last stages of DSE.

CONCLUSION

Measurement of CI by NICaS correlated well with Doppler derived CI. The calculation of Cpi and TPRi changes during dobutamine stress may provide important clinical information.

Detection of chest pain of non-cardiac origin at the emergency room by a new non-invasive device avoiding unnecessary admission to hospital

Recent advances in the treatment of acute coronary syndromes has raised awareness that prompt presentation for chest pain may be life saving. Most patients presenting with chest discomfort have a non-ischaemic ECG on presentation, but are routinely admitted to hospital because of diagnostic uncertainty for occult MI or ischaemia. We tested a new non-invasive device that measures central aortic pressure changes (dP/dtejc): an accepted index of myocardial performance that could be added to the diagnostic triage of ischaemia in the ER avoiding unnecessary admissions. We followed 85 patients presenting at the ER with acute chest pain. In 72 patients, negative ECG and myocardial enzyme dynamics ruled out coronary origin during the first 24 h after admission. In 8 of the 72 patients, coronary catheterisation found normal coronary arteries. In this group, average dP/dtejc was 163 (range 92-232). In 35 patients in whom the new non-invasive cardiac performance index dP/dtejc was above a threshold of >150, acute MI was ruled out. In 13 patients, acute chest pain had coronary origin confirmed by ECG and/or positive enzymes. The average dP/dtejc in this group was 117 (range 61-149). The dP/dtejc values were found to be significantly higher in patients without acute MI (p<0.001). Preliminary findings suggest that nearly 40% of patients presenting with acute chest pain could be spared the risks and costs of unnecessary hospital admission and more invasive cardiac testing by simply adding a easy to use, immediately obtained, test to the diagnostic protocol, and using a threshold of dP/dtejc>150 to rule out heart attack.

Plateletcrit, mean platelet volume, platelet distribution width: its expected values and correlation with parallel red blood cell parameters

The quantitation of platelets in peripheral blood is a well-recognized tool. Recently, new indices related to erythrocytes and platelet counts have been provided by hematologic analyzers. Concerning the platelet parameter, the three important parameters are plateletcrit (PCT), mean platelet volume (MPV), platelet distribution width (PDW). The purpose of the study is to investigate these three parameters to define their expected values and the correlation with the parallel red blood cell parameters, hematocrit (HCT), mean corpuscular volumer (MCV), and red blood cell distribution width (RDW). Blood samples form 215 volunteers were analyzed for platelet parameters using Technicon H*3. The average (mean +/- SD) values obtained with expected ranges were PCT 0.24 +/- 0.05% (range, 0.23-0.24%), MPV 12.79 +/- 5.91 fL (range, 12.39-13.19 fL), and PDW 46.79 +/- 2.70% (range, 46.61-46.97%). Concerning the correlation between PCT, MPV, and RDW and their parallel red blood cell parameters, there was no significant correlation between PCT and HCT, and between MPV and MCV. However, there was a significant correlation between PDW and RDW. It seems that the anisocytosis of red blood cells and platelets might co-occur. However, these data are basic observations; further in-depth evaluation of the platelet parameters is recommended.

Recent developments in cardiac output determination by bioimpedance: comparison with invasive cardiac output and potential cardiovascular applications

PURPOSE OF REVIEW

To describe recent developments in bioimpedance technique and its application in cardiovascular diseases. Cardiac output determination has been used selectively during recent years because of the need for invasive right heart catheterization. Hence, experience with its application in patients with cardiovascular diseases and especially heart failure is limited. Bioimpedance is a novel noninvasive technique determining changes in instantaneous (during one heartbeat) conductance of a small electrical current transferred through the body. By using different algorithms correcting for various body composition constants, it calculates the change in instantaneous arterial blood volume (that is, stroke volume) and cardiac output. Traditionally, bioimpedance cardiac output is determined using either thoracic or whole body techniques according to the location of the electrodes transmitting and receiving the small electrical current.

RECENT FINDINGS

Significant progress was achieved in recent years in cardiac output determination by bioimpedance. Newer algorithms using thoracic and whole body bioimpedance have demonstrated better correlation with invasive cardiac output determination. In a few preliminary studies bioimpedance-determined cardiac output was found useful in the diagnosis, risk stratification, and treatment titration of some cardiovascular conditions. Further, larger prospective studies are required to determine the true independent value of cardiac output measurement by bioimpedance for the evaluation of cardiovascular diseases and especially heart failure.

SUMMARY

Recently, significant improvement was achieved in cardiac output measurement by bioimpedance with both newer thoracic and whole body techniques. Preliminary studies imply that this measure may be of value in managing some cardiovascular disorders.

Accurate, Noninvasive Continuous Monitoring of Cardiac Output by Whole-Body Electrical Bioimpedance

STUDY OBJECTIVES

Cardiac output (CO) is measured but sparingly due to limitations in its measurement technique (ie, right-heart catheterization). Yet, in recent years it has been suggested that CO may be of value in the diagnosis, risk stratification, and treatment titration of cardiac patients, especially those with congestive heart failure (CHF). We examine the use of a new noninvasive, continuous whole-body bioimpedance system (NICaS; NI Medical; Hod-Hasharon, Israel) for measuring CO. The aim of the present study was to test the validity of this noninvasive cardiac output system/monitor (NICO) in a cohort of cardiac patients.

DESIGN

Prospective, double-blind comparison of the NICO and thermodilution CO determinations.

PATIENTS

We enrolled 122 patients in three different groups: during cardiac catheterization (n = 40); before, during, and after coronary bypass surgery (n = 51); and while being treated for acute congestive heart failure (CHF) exacerbation (n = 31). MEASUREMENTS AND INTERVENTION: In all patients, CO measurements were obtained by two independent blinded operators. CO was measured by both techniques three times, and an average was determined for each time point. CO was measured at one time point in patients undergoing coronary catheterization; before, during, and after bypass surgery in patients undergoing coronary bypass surgery; and before and during vasodilator treatment in patients treated for acute heart failure.

RESULTS

Overall, 418 paired CO measurements were obtained. The overall correlation between the NICO cardiac index (CI) and the thermodilution CI was r = 0.886, with a small bias (0.0009 +/- 0.684 L) [mean +/- 2 SD], and this finding was consistent within each group of patients. Thermodilution readings were 15% higher than NICO when CI was < 1.5 L/min/m(2), and 5% lower than NICO when CI was > 3 L/min/m(2). The NICO has also accurately detected CI changes during coronary bypass operation and vasodilator administration for acute CHF.

CONCLUSION

The results of the present study indicate that whole-body bioimpedance CO measurements obtained by the NICO are accurate in rapid, noninvasive measurement and the follow-up of CO in a wide range of cardiac clinical situations.

The role of cardiac power and systemic vascular resistance in the pathophysiology and diagnosis of patients with acute congestive heart failure

OBJECTIVE

Conventional hemodynamic indexes (cardiac index (CI), and pulmonary capillary wedge pressure) are of limited value in the diagnosis and treatment of patients with acute congestive heart failure (CHF).

PATIENTS AND METHODS

We measured CI, wedge pressure, right atrial pressure (RAP) and mean arterial blood pressure (MAP) in 89 consecutive patients admitted due to acute CHF (exacerbated systolic CHF, n=56; hypertensive crisis, n=5; pulmonary edema, n=11; and cardiogenic shock, n=17) and in two control groups. The two control groups were 11 patients with septic shock and 20 healthy volunteers. Systemic vascular resistance index (SVRi) was calculated as SVRi=(MAP-RAP)/CI. Cardiac contractility was estimated by the cardiac power index (Cpi), calculated as CIxMAP.

RESULTS AND DISCUSSION

We found that CI<2.7 l/min/m(2) and wedge pressure >12 mmHg are found consistently in patients with acute CHF. However, these measures often overlapped in patients with different acute CHF syndromes, while Cpi and SVRi permitted more accurate differentiation. Cpi was low in patients with exacerbated systolic CHF and extremely low in patients with cardiogenic shock, while SVRi was increased in patients with exacerbated systolic CHF and extremely high in patients with pulmonary edema. By using a two-dimensional presentation of Cpi vs. SVRi we found that these clinical syndromes can be accurately characterized hemodynamically. The paired measurements of each clinical group segregated into a specific region on the Cpi/SVRi diagnostic graph, that could be mathematically defined by a statistically significant line (Lambda=0.95). Therefore, measurement of SVRi and Cpi and their two-dimensional graphic representation enables accurate hemodynamic diagnosis and follow-up of individual patients with acute CHF.

Assessment of peripheral artery tonometry in the detection of treadmill exercise-induced myocardial ischemia

OBJECTIVES

We sought to assess the added diagnostic value of peripheral artery tonometric (PAT) measurements, based on finger pulsatile arterial volume changes, to standard 12-lead stress electrocardiography (ECG), for detecting exercise-induced myocardial ischemia, using single-photon emission computed tomography (SPECT) as the standard of comparison in a double-blinded, multicenter protocol.

METHODS

An automated algorithm for identifying myocardial ischemia from PAT was derived from 345 training cases. The PAT outcome was combined with the ECG result (ischemic, nonischemic, or equivocal), giving a PAT-enhanced value. A threshold of normality was determined to optimize agreement with the SPECT results in the training sample. The PAT-enhanced analysis was then validated in 616 subjects, only two of whom had technically unacceptable PAT studies.

RESULTS

In the validation cohort, receiver operating characteristic curve analysis of the PAT-enhanced diagnosis yielded an area under the curve of 0.72, a sensitivity of 63.5%, compared with 44.7% for ECG alone (p < 0.0001), and a specificity of 67.8% common to both ECG and PAT-enhanced diagnoses. Similar results were found in the training sample. Although over 10% of validation subjects had equivocal ECG results, with the aid of PAT, it was possible to provide diagnostic information for all but one subject.

CONCLUSIONS

Peripheral artery tonometry may be useful for improving the diagnosis of exercise-induced myocardial ischemia by both enhancing the sensitivity without impairing the specificity and increasing the percentage of definitive test results.

Diastolic aortic pressure rise during percutaneous transluminal coronary angioplasty: an index of left ventricular systolic dysfunction

OBJECTIVES

To investigate the relation between diastolic aortic pressure response and left ventricular systolic dysfunction during percutaneous transluminal coronary angioplasty.

BACKGROUND

The abnormal diastolic blood pressure rise during exercise in patients with coronary artery disease probably reflects left ventricular systolic dysfunction rather than the number of stenosed coronary arteries.

METHODS

Aortic blood pressures and left ventricular systolic function indices were estimated in 26 patients with single proximal stenosis of the left anterior descending coronary artery both before and during angioplasty.

RESULTS

During coronary angioplasty all patients presented an increase in diastolic aortic pressure (P << 0.001), 8-12s before intracoronary electrocardiographic changes. During acute ischaemia there was a decrease in left ventricular ejection fraction (P << 0.001) and stroke volume (P << 0.001) and an increase in end systolic volume (P << 0.001) and left ventricular end diastolic pressure (P << 0.001). No statistically significant changes were observed in systolic blood pressure or heart rate. The aortic diastolic pressure increase was correlated with the decrease in ejection fraction (r = -0.95, P << 0.001) and with the increases in end systolic volume (r = 0.86, P << 0.001) and left ventricular end diastolic pressure (r = 0.85, P << 0.001).

CONCLUSIONS

The rise in diastolic aortic pressure during percutaneous transluminal coronary angioplasty occurs earlier than intracoronary electrocardiographic changes and is related to ischaemic left ventricular systolic dysfunction.

Correlation between myocardial ischemia and changes in arterial resistance during coronary artery bypass surgery

The arterial resistometer provides continuous on-line monitoring of changes in arterial resistance. Resistance index (Ri), which bears a direct relationship to systemic vascular resistance (SVR), is defined by the equation Ri = P'/(dP'/dt), where dP'/dt is the peak dP/dt of the arterial waveform, and P' is the pressure at dP'/dt. In 42 patients with unstable angina, changes in Ri were studied at six periods during aortocoronary bypass surgery before tracheal intubation, during tracheal intubation, leg elevation, presternotomy, sternotomy, and dissection of the internal mammary artery. Thirty-four episodes of ischemia (0.1 mV ST segment changes) were observed in 26 patients. All ischemic episodes were associated with increased Ri (mean increase, 102 +/- 52%). Elevation of the pulmonary capillary wedge pressure correlated with ischemia during the preintubation, intubation, and sternotomy periods, but not in the remaining periods. Changes in arterial pressure and heart rate were not good predictors of ischemia. The prevalence of ST segment changes increased markedly during all periods of anesthesia with increase in Ri (P less than 0.05). Ninety-one percent of ST segment changes were associated with a 25% increase from the baseline Ri. Raising the cutoff point to a greater than or equal to 75% increase in Ri improved the specificity of Ri in ischemia detection from 61% to 92%. An increase of greater than or equal to 75% in Ri occurred in only 8% of cases without ST segment changes. It was found that an increase in Ri as depicted by the arterial resistometer was the best hemodynamic correlate of myocardial ischemia.