Väinö Turjanmaa

Non-invasive measurement of cardiac output: whole-body impedance cardiography in simultaneous comparison with thermodilution and direct oxygen Fick methods

ObjectiveTo determine the reliability of whole-body impedance cardiography (ICGWB), with electrodes attached to wrists and ankles, in the measurement of cardiac output (CO) on the basis of simultaneous comparison with thermodilution (TD) and direct oxygen Fick (Fick) methods.DesignProspective clinical study.SettingA surgical intensive care unit at a university hospital.PatientsThirty consecutive subjects undergoing a coronary artery bypass surgery were investigated preoperatively.MeasurementsICGWB derived CO was measured simultaneously with the TD and Fick methods to establish the biases and limits of agreement (LA) between the methods.ResultsThe results obtained by ICGWB and the invasive methods showed good agreement. The bias and LA between COTD and COICG were 0.001/min; −1.37 and 1.37 1/min, respectively, and were close to those obtained between COTD and COFICK, 0.321/min; 1.74 and −1.101/ min. The bias and LA between the COFICK and COICG were −0.32 1/min; −2.24 and 1.60 1/min respectively. The repeatability value of consecutive single measurements for ICGWB (RVICG=0.571/min) was much better than for the TD method (RVTD=1.10 1/min).ConclusionThere was close agreement between the results of the three methods in the measurement of CO. In sedated preoperative patients the accuracy of ICGWB is within clinically acceptable limits and its repeatability is excellent. ICGWB provides a useful alternative to the TD and Fick methods in cases where the pressures supplied by the pulmonary artery catheter are not essential.

Simultaneous non-invasive assessment of arterial stiffness and haemodynamics - a validation study.

The purpose of the study was to estimate the reliability of whole‐body impedance cardiography (ICGWB)‐derived pulse wave velocity (PWV) and stroke volume index to pulse pressure (SI/PP) measurements. The repeatability and reproducibility of ICGWB parameters were also determined. Agreement between the impedance and Doppler ultrasound‐based PWV measurements was estimated in 25 healthy subjects in two consecutive measurements. Impedance‐derived SI/PP (SIICG/PP) estimates were compared with simultaneously measured SI/PP based on thermodilution (SITD/PP) and direct Fick (SIFICK/PP) methods in 30 surgical patients. PWV measured between the aortic arch and popliteal artery using the impedance technique with selective electrode configuration (PWVIS) agreed well with the Doppler ultrasound method (PWVDOPP), the bias (PWVDOPP – PWVIS) and precision (± SD of differences) being 0·00 and 0·79 m s−1, respectively. PWV derived from the whole‐body and popliteal impedance plethysmograms (PWVICG) overestimated slightly PWVDOPP values. The repeatability value for PWVIS was excellent, being 0·54 m s−1. The reproducibility values for PWVDOPP and PWVIS were very similar (2·17 and 2·42 m s−1, respectively). Changes in PWVIS correlated strongly with changes in PWVDOPP (r=0·74; P<0·0001), indicating that both methods reflected the true physiological variation in PWV. The agreement between SIICG/PP and SITD/PP or SIFICK was almost identical to the agreement between the SITD/PP and SIFICK/PP. In conclusion,whole‐body impedance cardiography provides handy and reliable means of evaluating arterial stiffness on the basis of PWV and SI/PP simultaneously with conventional haemodynamic parameters. The method is highly repeatable and reproducible.

Diagnostic Accuracies of Plasma Creatinine, Cystatin C, and Glomerular Filtration Rate Calculated by the Cockcroft–Gault and Levey (MDRD) Formulas

Estimation of the glomerular filtration rate (GFR) is the most widely used test of renal function, reflecting the relative mass of functional renal tissue and thus the number of functioning nephrons. Methods based on measurement of exogenous substances such as inulin, 51Cr-EDTA, 99mTc-diethylenetriaminepentaacetic acid, and iohexol are accurate but too complex and laborious for routine clinical use; thus, measurement of endogenous blood substances is common practice. Plasma or serum creatinine and its renal clearance are the approaches most commonly used despite their acknowledged unreliability. Cystatin C, a small basic protein, has been proposed as a better marker than creatinine. Recently, the value of cystatin C was thoroughly reviewed in this Journal (1), and according to this review and a new metaanalysis (2), most studies have concluded that cystatin C is superior to plasma creatinine, whereas several authors have concluded that cystatin C provides no advantage. One purpose of the present study was to clarify possible reasons for the earlier, partly conflicting results. A recently published guideline from the National Kidney Foundation (3) recommended that GFR be estimated from prediction equations taking into account the serum creatinine concentration and some or all of the following variables: age, gender, race, and body size. We therefore also compared cystatin C with GFRs calculated by the Cockcroft–Gault (4) and the MDRD(5) formulas. We studied 112 patients (55 men and 57 women) for whom 51Cr-EDTA clearance had been requested. The mean age of the patients was 57.0 years (range, 17–89 years). Body mass index (BMI) was 15.2–42.4 kg/m2, and 51 …

Increased bronchial nitric oxide production in patients with asthma measured with a novel method of different exhalation flow rates

The concentration of nitric oxide (NO) in exhaled air is increased in patients with asthma, suggesting that measuring fractional exhaled NO concentration (FENO) may be used to monitor asthmatic airway inflammation. However, increased FENO is not specific for asthma, as other inflammatory lung diseases may also increase FENO. To augment the specificity of FENO measurement, we tested a novel theoretical modelling of pulmonary NO dynamics that allows the approximation of alveolar NO concentration and bronchial NO flux separately by measuring FENO at several exhalation flow rates. We measured FENO at four exhalation flow rates in 10 steroid-naive asthmatics, 5 patients with extrinsic allergic alveolitis, and in 10 healthy controls. Both the asthmatics and the patients with alveolitis had significantly higher FENO than the healthy controls. The increased NO concentration originated from the bronchial level in the asthmatics and from the alveolar level in the patients with alveolitis. In the second part of the study we assessed the repeatability of FENO test, within-day and day-to-day (during two weeks) variation in FENO, and the effects of mouth pressure and cigarette smoking on FENO in healthy volunteers. Repeatability of 10 subsequent measurements was high (coefficient of variation (CV) 4.6% ± 0.4%), and no diurnal variation was found. The day-to-day variation during a 2-week period gave a CV of 10.6% ± 1.0%. The magnitude of mouth pressure (5-20 cmH2O in adults, 5-40 cmH2O in children) during measurement had no effect on FENO. Smoking a cigarette caused a small and transient but statistically significant increase in FENO at 1 and 5 min after smoking. In conclusion, FENO measurement is highly repeatable with low day-to-day variation among healthy subjects. Our results also suggest that the present novel method of measuring FENO at several exhalation flow rates can be used to approximate alveolar and bronchial contributions to FENO separately and thus increase the clinical value of this test.

Short-term variability of blood pressure and heart rate in borderline and mildly hypertensive subjects.

Electrocardiogram and intra-arterial blood pressure were recorded in 96 men (aged 35 to 45 years) by the Oxford method over a 30-hour period. The study involved 33 normotensive, 29 borderline hypertensive, and 34 mildly hypertensive individuals, as assessed by the cuff method. Five-minute periods during sleep and with subjects in supine, sitting, and standing positions were extracted from the recordings for frequency domain analysis. Power spectrum density estimates of systolic blood pressure, diastolic blood pressure, and heart rate were calculated by an autoregressive method over the bandwidths of 0.02 to 0.075 (low-frequency), 0.075 to 0.15 (midfrequency), and 0.15 to 0.35 Hz (high-frequency), attributable to thermoregulatory, baroreceptor, and respiratory activity. No significant intergroup differences were observed at nighttime, but in different body positions the borderline hypertensive subjects frequently had either greater low-frequency variability or smaller midfrequency variability than the other groups. In this respect, the power spectra for systolic and diastolic blood pressures provided better statistical differentiation between the groups than those for heart rate. Furthermore, the borderline hypertensive subjects exhibited attenuated night-day changes in the low-frequency band for all time series. The results suggest that in borderline hypertension the baroreceptor oscillations are shifted to lower frequencies, presumably reflecting altered function of the sympathetic nervous system. In conclusion, spectral analysis of blood pressure variability for controlled test situations made it possible to detect differences in the cardiovascular regulatory systems between normotensive, borderline hypertensive, and mildly hypertensive individuals.

Accurate detection of coronary artery disease by integrated analysis of the ST-segment depression/heart rate patterns during the exercise and recovery phases of the exercise electrocardiography test

In this comparative cross-sectional study, we evaluated whether a novel computerized diagnostic variable, ST-segment depression/heart rate ST/HR analysis during both the exercise and postexercise recovery phases of the exercise electrocardiography (ECG) test, can detect coronary artery disease more accurately than methods using either exercise or recovery phase alone. The study population comprised 347 clinical patients referred for a routine bicycle exercise ECG test at Tampere University Hospital, Finland. Of these, 127 had angiographically proven coronary artery disease, whereas 13 had no coronary artery disease according to angiography, 18 had no perfusion defect according to technetium-99m sestamibi single-photon emission computed tomography, and 189 were clinically normal with respect to cardiac diseases. For each patient, the maximum values of the ST/HR hysteresis, ST/HR index, end-exercise ST depression, and recovery ST depression were determined from the Mason-Likar modification of the standard 12-lead exercise electrocardiogram [aVL, aVR, and V1 excluded]. The diagnostic performance of these continuous diagnostic variables was compared by means of receiver-operating characteristic analysis. The area under the receiver-operating characteristic curve of the ST/HR hysteresis was 89%, which was significantly larger than that of the end-exercise ST depression (76%, p < or = 0.0001), recovery ST depression (84%, p = 0.0063), or ST/HR index (83%, p = 0.0023), indicating superior diagnostic performance of the ST/HR hysteresis independent of the partition value selection. In conclusion, computerized analysis of the HR-adjusted ST depression pattern during the exercise phase, integrated with the HR-adjusted ST depression pattern during the recovery phase after exercise, can significantly improve the diagnostic performance and clinical utility of the exercise ECG test for the detection of coronary artery disease.

Enhanced Predictive Power of Quantitative TWA during Routine Exercise Testing in the Finnish Cardiovascular Study

Introduction: We examined whether quantification of T‐wave alternans (TWA) enhances this parameters capacity to evaluate the risk for total and cardiovascular mortality and sudden cardiac death (SCD).

Combined assessment of heart rate recovery and T-wave alternans during routine exercise testing improves prediction of total and cardiovascular mortality: the Finnish Cardiovascular Study.

BACKGROUND Identification of individuals who are at risk for cardiovascular death remains a pressing public health challenge. Derangements in autonomic function acting upon an electrically unstable substrate are thought to be critical elements in triggering cardiovascular events. OBJECTIVE The purpose of this study was to analyze heart rate recovery (HRR) in combination with T-wave alternans (TWA) to improve risk assessment. METHODS The Finnish Cardiovascular Study (FINCAVAS) enrolled consecutive patients (N = 1,972 [1,254 men and 718 women], age 57 +/- 13 years [mean +/- SD]) with a clinically indicated exercise test using bicycle ergometer. TWA was analyzed continuously with the time-domain modified moving average method. Maximum TWA at heart rates <125 bpm was derived. RESULTS During 48 +/- 13 months of follow-up (mean +/- SD), 116 patients died; 55 deaths were cardiovascular. In multivariable Cox analysis after adjustment for common coronary risk factors, high exercise-based TWA (> or =60 microV) and low HRR (< or =18 bpm) yielded relative risks for all-cause mortality of 5.0 (95% confidence 2.1-12.1, P <.01) and for cardiovascular mortality of 12.3 (95% confidence interval 4.3-35.3, P <.01). High recovery-based TWA (> or =60 microV) and low HRR (< or =18 bpm) yielded relative risks for all-cause death of 6.1 (95% confidence interval 2.8-13.2, P <.01) and for cardiovascular mortality of 8.0 (95% confidence interval 2.9-22.0, P <.01). Prediction by HRR and TWA, both singly and in combination, exceeded that of standard cardiovascular risk factors. CONCLUSION Reduced HRR and heightened TWA powerfully predict risk for cardiovascular and all-cause death in a low-risk population. This novel approach could aid in screening of general populations during routine exercise protocols as well as improve insights into pathophysiology.

Pulse wave velocity reference values in healthy adults aged 26–75 years

The stiffening of arteries is associated with various cardiovascular diseases. Arterial stiffening can be studied utilizing arterial pulse wave velocity (PWV), but the absence of reliable reference values for PWV has limited its use in clinical practice. The aim of this study was to establish a range of reference values for PWV. PWV was examined by measuring the time difference of systolic pulse waves in arteries from the aortic arch to the popliteal artery using whole‐body impedance cardiography (ICG). The study population consisted of 799 individuals (age range 25–76 years), 283 of whom had no evidence of cardiovascular disease, and a low burden of risk factors was selected to represent an apparently healthy population. In healthy study population, PWV was higher in males (8·9 ± 1·8 m s−1) than females (8·1 ± 2·0 m s−1, P<0·001). Young males had lower PWV values than old males. Correspondingly, young females also had lower PWV values than old females. PWV was clearly associated with age, and PWV was higher in young and middle‐aged males than in females. There was no statistically significant difference between old males and females in PWV. In conclusion, whole‐body ICG provides a practical method for PWV measurement. Reference values can be useful in the clinical management of patients, especially in detecting early vascular disease or an increased risk of cardiovascular complications.

The Finnish Cardiovascular Study (FINCAVAS): characterising patients with high risk of cardiovascular morbidity and mortality

BackgroundThe purpose of the Finnish Cardiovascular Study (FINCAVAS) is to construct a risk profile – using genetic, haemodynamic and electrocardiographic (ECG) markers – of individuals at high risk of cardiovascular diseases, events and deaths.Methods and designAll patients scheduled for an exercise stress test at Tampere University Hospital and willing to participate have been and will be recruited between October 2001 and December 2007. The final number of participants is estimated to reach 5,000. Technically successful data on exercise tests using a bicycle ergometer have been collected of 2,212 patients (1,400 men and 812 women) by the end of 2004. In addition to repeated measurement of heart rate and blood pressure, digital high-resolution ECG at 500 Hz is recorded continuously during the entire exercise test, including the resting and recovery phases. About 20% of the patients are examined with coronary angiography. Genetic variations known or suspected to alter cardiovascular function or pathophysiology are analysed to elucidate the effects and interactions of these candidate genes, exercise and commonly used cardiovascular medications.DiscussionFINCAVAS compiles an extensive set of data on patient history, genetic variation, cardiovascular parameters, ECG markers as well as follow-up data on clinical events, hospitalisations and deaths. The data enables the development of new diagnostic and prognostic tools as well as assessments of the importance of existing markers.