[ECG-gated chest CT angiography: value for atypical chest pain evaluation]

PURPOSE: The aim of this study was to evaluate ECG-gated whole chest CTA as a routine triage tool for patients with acute chest pain. MATERIAL AND METHODS: Whole chest CTA with retrospective ECG-gating was performed in 30 patients with acute atypical chest pain. The ten main segments of the coronary arteries, the pulmonary arteries, the aorta, and the myocardium (function, morphology) were independently analyzed by a resident and two senior radiologists. The inter-observer agreement between resident and senior radiologists was calculated. A final diagnosis was determined by consensus. RESULTS: Thirty patients were included. The coronary artery segments, myocardium and pulmonary arteries were considered analyzable in 84%, 90% and 97% of cases respectively. A final diagnosis for the cause of pain was retained in 19 patients: significant coronary artery stenosis (5), pulmonary embolus (5), aortic dissection (1), hypokinetic cardiomyopathy (2), lung parenchymal abnormalities (5), and hiatus hernia (1). Inter-observer agreement ranged from 0.76 to 1 between senior radiologists and from 0.76 to 1 between resident and senior radiologists. The average time of image interpretation ranged from 14 to 15 minutes. CONCLUSION: ECG-gated whole chest CT angiography appears as a promising tool for the evaluation of acute chest pain. Combined evaluation of appearance and function of the myocardium can reveal additional interesting information.

The optimal lead insertion depth for esophageal ECG recordings with respect to atrial signal quality

BACKGROUND Diagnosing supraventricular arrhythmias by conventional long-term ECG can be cumbersome because of poor p-waves. Esophageal long-term electrocardiography (eECG) has an excellent sensitivity for atrial signals and may overcome this limitation. However, the optimal lead insertion depth (OLID) is not known. METHODS We registered eECGs at different lead insertion depths in 27 patients and analyzed 199,716 atrial complexes with respect to signal amplitude and slope. Correlation and regression analyses were used to find a criterion for OLID. RESULTS Atrial signal amplitudes and slopes significantly depend on lead insertion depth. OLID correlates with body height (rSpearman=0.71) and can be estimated by OLID [cm]=0.25*body height[cm]-7cm. At this insertion depth, we recorded the largest esophageal atrial signal amplitudes (1.27±0.86mV), which were much larger compared to conventional surface lead II (0.19±0.10mV, p<0.0001). CONCLUSION The OLID depends on body height and can be calculated by a simple regression formula.

Simultaneous registration of ECG and cardiac motion by a single esophageal probe

Long-term surface ECG is routinely used to diagnose paroxysmal arrhythmias. However, this method only provides information about the heart's electrical activity. To this end, we investigated a novel esophageal catheter that features synchronous esophageal ECG and acceleration measurements, the latter being a record of the heart's mechanical activity. The acceleration data were quantified in a small study and successfully linked to the activity sequences of the heart in all subjects. The acceleration signals were additionally transformed into motion. The extracted cardiac motion was proved to be a valid reference input for an adaptive filter capable of removing relevant baseline wandering in the recorded esophageal ECGs. Taking both capabilities into account, the proposed recorder might be a promising tool for future long-term heart monitoring.

Asynchronous ECG time sampling: Saving bits with Golomb-Rice encoding

We present a technique for online compression of ECG signals using the Golomb-Rice encoding algorithm. This is facilitated by a novel time encoding asynchronous analog-to-digital converter targeted for low-power, implantable, long-term bio-medical sensing applications. In contrast to capturing the actual signal (voltage) values the asynchronous time encoder captures and encodes the time information at which predefined changes occur in the signal thereby minimizing the sensor's energy use and the number of bits we store to represent the information by not capturing unnecessary samples. The time encoder transforms the ECG signal data to pure time information that has a geometric distribution such that the Golomb-Rice encoding algorithm can be used to further compress the data. An overall online compression rate of about 6 times is achievable without the usual computations associated with most compression methods.

Towards End-User Driven Power Saving Control in Android devices

Abstract. During the last decade mobile communications increasingly became part of people's daily routine. Such usage raises new challenges regarding devices' battery lifetime management when using most popular wireless access technologies, such as IEEE 802.11. This paper investigates the energy/delay trade-off of using an end-user driven power saving approach, when compared with the standard IEEE 802.11 power saving algorithms. The assessment was conducted in a real testbed using an Android mobile phone and high-precision energy measurement hardware. The results show clear energy benefits of employing user-driven power saving techniques, when compared with other standard approaches.

Costs and yield of a 15-month preparticipation cardiovascular examination with ECG in 1070 young athletes in Switzerland: implications for routine ECG screening

Background The usefulness and modalities of cardiovascular screening in young athletes remain controversial, particularly concerning the role of 12-lead ECG. One of the reasons refers to the presumed false-positive ECGs requiring additional examinations and higher costs. Our study aimed to assess the total costs and yield of a preparticipation cardiovascular examination with ECG in young athletes in Switzerland. Methods Athletes aged 14–35 years were examined according to the 2005 European Society of Cardiology (ESC) protocol. ECGs were interpreted based on the 2010 ESC-adapted recommendations. The costs of the overall screening programme until diagnosis were calculated according to Swiss medical rates. Results A total of 1070 athletes were examined (75% men, 19.7±6.3 years) over a 15-month period. Among them, 67 (6.3%) required further examinations: 14 (1.3%) due to medical history, 15 (1.4%) due to physical examination and 42 (3.9%) because of abnormal ECG findings. A previously unknown cardiac abnormality was established in 11 athletes (1.0%). In four athletes (0.4%), the abnormality may potentially lead to sudden cardiac death and all of them were identified by ECG alone. The cost was 157 464 Swiss francs (CHF) for the overall programme, CHF147 per athlete and CHF14 315  per finding. Conclusions Cardiovascular preparticipation examination in young athletes using modern and athlete-specific criteria for interpreting ECG is feasible in Switzerland at reasonable cost. ECG alone is used to detect all potentially lethal cardiac diseases. The results of our study support the inclusion of ECG in routine preparticipation screening.

Should we perform a screening ECG among asymptomatic adults?

The resting ECG is a safe, low cost and widely available in the clinical investigation of several cardiac symptoms. However, there is controversy regarding the use as a screening tool or routine cardiovascular (CV) risk assessment test among healthy asymptomatic adults. Two recent studies reported that ECG adds supplemental information in the estimation of coronary artery disease (CAD) risk in asymptomatic patients, especially in those with intermediate risk. However, we currently need more data on the impact of ECG on the prevention of clinical CV outcomes, especially in a randomized clinical trial, and on additional costs of testing and treatment. For the time being, routine ECG testing is not recommended for the prevention of CV events among healthy asymptomatic adults.

Bufferless Compression of Asynchronously Sampled ECG Signals in Cubic Hermitian Vector Space.

Asynchronous level crossing sampling analog-to-digital converters (ADCs) are known to be more energy efficient and produce fewer samples than their equidistantly sampling counterparts. However, as the required threshold voltage is lowered, the number of samples and, in turn, the data rate and the energy consumed by the overall system increases. In this paper, we present a cubic Hermitian vector-based technique for online compression of asynchronously sampled electrocardiogram signals. The proposed method is computationally efficient data compression. The algorithm has complexity O(n), thus well suited for asynchronous ADCs. Our algorithm requires no data buffering, maintaining the energy advantage of asynchronous ADCs. The proposed method of compression has a compression ratio of up to 90% with achievable percentage root-mean-square difference ratios as a low as 0.97. The algorithm preserves the superior feature-to-feature timing accuracy of asynchronously sampled signals. These advantages are achieved in a computationally efficient manner since algorithm boundary parameters for the signals are extracted a priori.