DCM-PROGRESS: predicting end-stage heart failure in non-ischemic dilated cardiomyopathy patients.

Aims: Patients with non-ischemic dilated cardiomyopathy (DCM) are at considerable risk for end-stage heart failure (HF), requiring close monitoring to identify early signs of disease. We aimed to develop a model to predict the 5-years risk of end-stage HF, allowing for tailored patient monitoring and management. Methods and results: Derivation data were available from a Dutch cohort of 293 DCM patients, with external validation available from a Czech Republic cohort of 235 DCM patients. Candidate predictors spanned patient and family histories, ECG and echocardiogram measurements, and biochemistry. End-stage HF was defined as a composite of death, heart transplantation, or implantation of a ventricular assist device. Lasso and sigmoid kernel support vector machine (SVM) algorithms were trained using cross-validation. During follow-up 65 (22%) of Dutch DCM patients developed end-stage HF, with 27 (11%) cases in the Czech cohort. Out of the two considered models, the lasso model (retaining NYHA class, heart rate, systolic blood pressure, height, R-axis, and TAPSE as predictors) reached the highest discriminative performance (testing c-statistic of 0.85, 95%CI 0.58; 0.94), which was confirmed in the external validation cohort (c-statistic of 0.75, 95%CI 0.61; 0.82), compared to a c-statistic of 0.69 for the MAGGIC score. Both the MAGGIC score and the DCM-PROGRESS model slightly over-estimated the true risk, but were otherwise appropriately calibrated. Conclusion: We developed a highly discriminative risk-prediction model for end-stage HF in DCM patients. The model was validated in two countries, suggesting the model can meaningfully improve clinical decision-making.

Respiratory-induced hemodynamic changes measured by whole-body multichannel impedance plethysmography.

The cardiovascular system is described by parameters including blood flow, blood distribution, blood pressure, heart rate and pulse wave velocity. Dynamic changes and mutual interactions of these parameters are important for understanding the physiological mechanisms in the cardiovascular system. The main objective of this study is to introduce a new technique based on parallel continuous bioimpedance measurements on different parts of the body along with continuous blood pressure, ECG and heart sound measurement during deep and spontaneous breathing to describe interactions of cardiovascular parameters. Our analysis of 30 healthy young adults shows surprisingly strong deep-breathing linkage of blood distribution in the legs, arms, neck and thorax. We also show that pulse wave velocity is affected by deep breathing differently in the abdominal aorta and extremities. Spontaneous breathing does not induce significant changes in cardiovascular parameters.

Can we hear ventricle dyssynchrony? Yes, we can.

This study introduces a method for detection of ventricular depolarization activity and the transfer of this activity into an audible stereo audio signal. Heart potentials are measured by an ultra-high-frequency high-dynamic-range electrocardiograph (UHF-ECG) with a 25-kHz sampling rate. Averaged and prolonged UHF amplitude envelopes of V1-3 and V4-6 leads at a frequency range of 500-1000 Hz are used as a modulating function for two carrier audio frequencies. The right speaker makes it possible to listen to the depolarization of the septum and right ventricle (V1-3) and the left speaker the left ventricle lateral wall (V4-6). In the healthy heart, both speakers can be heard simultaneously. A delayed L or R speaker represents the dyssynchronous electrical activation of the ventricles. Examples of the normal heart, right bundle branch block and left bundle branch block can be heard at www.medisig.com/uhfecg.

Respiratory induced heart rate and blood pressure variability during mechanical ventilation in critically ill and brain death patients.

UNLABELLED: We analysed respiratory induced heart rate and blood pressure variability in mechanically ventilated patients with different levels of sedation and central nervous system activity. Our aim was to determine whether it is possible to distinguish different levels of sedation or human brain activity from heart rate and blood pressure. We measured 19 critically ill and 15 brain death patients ventilated at various respiratory frequencies - 15, 12, 8 and 6 breaths per minute. Basal and deeper sedation was performed in the critically ill patients. We detected and analysed heart rate and blood pressure parameters induced by ventilation. RESULTS: Respiratory induced heart rate variability is the unique parameter that can differentiate between brain death patients and sedated critically ill patients. Significant differences exist, especially during slow deep breathing with a mean period of 10 seconds. The limit values reflecting brain death are: baroreflex lower than 0.5 ms/mmHg and tidal volume normalised heart rate variability lower than 0.5 ms/ml. Reduced heart rate variability parameters of brain death patients remain unchanged even after normalisation to respiration volume. However, differences between basal and deep sedation do not appear significant on any parameter.

Excitation specificity of repolarization parameters.

UNLABELLED: The excitation specificity of QT dynamic parameters was tested on three groups of subjects: healthy subjects; non-medicated hypertensive subjects with metabolic syndrome; and subjects with essential hypertension. Four different excitations of RR were used: bicycling exercise; tilt with breathing 0.1 and 0.33 Hz; and deep breathing. Linear dynamic feedback model of QT/RR coupling was supposed at the analysis and next repolarization parameters were tested: QTc; gain of QT/RR coupling for slow and fast RR variability; time constant of QT adaptation; and random QT variability. RESULTS: Dynamic repolarization parameters statistically significantly depend on the type of RR excitation. The gain of QT/RR coupling for slow RR variability, the time constant of QT adaptation and QTc are maximal at RR excitation given by the bicycling exercise. The frequency of breathing, i.e. corresponding vagal modulation has no effect on repolarization parameters. The measurements with deep breathing, without any other slow excitation of heart rate, has low signal-to-noise ratio of analyzed data and resulting QT parameters are inaccurate. CONCLUSION: The use of heart rate excitation and all measurements conditions should be defined for the exact analysis of the repolarization dynamic parameters.

Blood pressure dynamics in hypertensive subjects during tilt table test.

Blood pressure dynamicity during tilt table measurement is discussed. We analyzed ECG and BP parameters from 14 normotensive young healthy volunteers, 15 old healthy volunteers, and two groups of hypertensive patients--20 non-medicated hypertensive subjects with no other known complications and 21 hypertensive non-medicated subjects with confirmed obesity (according to waist circumference), hyperlipidemia or diabetes mellitus. The dynamic parameters, such as pulse pressure, maximum of derivative BP, difference between maximum and minimum of derivative BP and SBP peak--DBP depression time were obtained from derivative continuous blood pressure signal recordings. We have found that the age factor plays a more significant role in dynamic parameters change and in inter-group differentiation than additional risk factors of hypertensive subjects.

[Can we cure atrial flutter with radiofrequency ablation in an hour?]. / Je mozné vylécit typický flutter síní radiofrekvencní ablací do jedné hodiny?

BACKGROUND: Radiofrequency ablation of common atrial flutter requires the creation of a complete transmural ablation line across cavotricuspid region to achieve bidirectional conduction block. Irrigated tip catheters facilitate rapid achievement of this block by creation larger and deeper lesions. The EASTHER registry was organized to collect data about the efficacy of the procedure in small and middle volume centres in Central and Eastern Europe, all using THERMOCOOL catheter technology. METHODS: Easther is a prospective registry (April 2002-February 2003). 133 consecutive patients (81.1% male, age 59.0 +/- 10.4 years, range 30-81 years) with common atrial flutter were enrolled. Coincidence with atypical flutter was observed in 2.7%. Patients had a history of flutter of 31.0 +/- 53.6 month (range 1-403) and concomitant atrial fibrillation was observed in 42.9%. Structural heart disease was present in 38.9%. Amount of re-ablated cases was 14%. RF energy was applied during 60 sec in power-controlled mode at a setting between 40 to 50 W with an average flow rate of 19.0 ml/min. RESULTS: Acute success rate defined as bi-directional block was achieved in 93.1%, although 94.7% of cases were assessed successful by the treating electrophysiologist. Average number of RF applications was 12.0 +/- 7.0 (range 2-40) per procedure. Average delivered power varied between a minimum of 36.1 +/- 15.1 W till a maximum of 45.3 +/- 13.0 W, while the average maximum temperature observed at the same time was varied between 39.0 +/- 3.4 degrees C and 45.4 +/- 4.0 degrees C. Total procedure time was 100.1 +/- 42.7 min (range 20-280 min) and fluoroscopy time was 15.8 +/- 9.6 min (range 4-45 min). In comparable French TC registry Average total and fluoroscopy time were 46.4 +/- 33.6 min, and 10.0 +/- 6.8 min resp. In the Middle European centres total and fluoroscopy time was 96.1 +/- 40.9 min, and 15.0 +/- 8.9 min resp. In centres from Eastern Europe it was 120.3 +/- 51.2 min, and 20.4 +/- 11.9 min resp. Two adverse events were reported. Both patients had strong chest pain during ablation. These results are comparable with the literature data published. CONCLUSIONS: Irrigated tip catheters are effective and safe in ablation of common atrial flutter. This technology helps to accelerate and facilitate achievement of bi-directional isthmus block. Most of procedures were terminated to one hour in experienced centers in France as early as 2002. Procedures not exceeding one hour are feasible in case of spreading this method as method of first choice with gaining of experiences in centres of Middle and Eastern Europe.

Noninvasive detection of vessel stiffness from continuous blood pressure recordings in hypertensive subjects.

This paper presents results of blood pressure dynamicity analysis aimed at vessel stiffness detection and subsequent cardiac risk stratification. We analyzed ECG and BP parameters from 12 normotensive young healthy volunteers, 10 old healthy volunteers, and two groups of hypertensive patients -- 12 young non-medicated hypertensive subjects with no other known complications and 16 hypertensive non-medicated subjects with confirmed obesity (according to waist circumference), hyperlipidemia or diabetes mellitus. The dynamic parameters obtained from a derivative continuous blood pressure signal provide additional information about vessel compliance. They can differentiate hypertensive subjects according to the level of cardiovascular risk.