Simple regional strain pattern analysis to predict response to cardiac resynchronization therapy: rationale, initial results, and advantages.

BACKGROUND: A classical strain pattern of early contraction in one wall and prestretching of the opposing wall followed by late contraction has previously been associated with left bundle branch block (LBBB) activation and short-term response to cardiac resynchronization therapy (CRT). Aims of this study were to establish the long-term predictive value of an LBBB-related strain pattern and to identify changes in contraction patterns during short-term and long-term CRT. METHODS AND RESULTS: Sixty-seven patients with standard CRT criteria were prospectively enrolled between early 2009 and late 2010. Echocardiography including regional strain analysis by 2-dimensional speckle tracking was performed 1 week before implantation, at day 1, and 6 months after. Response was defined as a decrease in left ventricular end-systolic volume ≥ 15%. The predictive ability of a classical pattern was compared with time-to-peak measurements from velocity and deformation analysis. Forty-three patients (65%) were classified as responders. The presence of a classical pattern showed 91% specificity and 95% sensitivity for response and performed significantly better than time-to-peak parameters in prediction of response to CRT (P < .001, all). In responders, CRT acutely increased septal longitudinal peak systolic strain (-8.7% ± 3.6% to -11.1% ± 3%, P < .001) but not in nonresponders. CONCLUSIONS: The classical pattern is highly predictive of response to CRT and superior to time-to-peak methods. Patients who obtain long-term reverse remodeling are characterized by short-term reversal of the classical strain pattern. These findings emphasize the value of recognizing potentially reversible strain patterns in selection of CRT candidates.

[Severe hyperventilation as a differential diagnosis of acute coronary syndrome]. / Svaer hyperventilation som differentialdiagnose til akut koronarsyndrom.

We report a case where a 30-year-old, otherwise healthy female was admitted to hospital with symptoms of hyperventilation, including chest discomfort and an abnormal ECG showing ST depressions and T-wave inversions. The ECG changes disappeared spontaneously during the next 24 hours as the patient was calmed down. A few weeks after discharge, the ECG changes were partially reproduced during a six-minute hyperventilation test. It is worth remembering that severe hyperventilation can cause ECG changes similar to those seen in acute coronary syndrome.

Reproducibility of heart rate variability, blood pressure variability and baroreceptor sensitivity during rest and head-up tilt.

OBJECTIVE: Previous studies have indicated moderate-to-poor reproducibility of heart rate variability (HRV) but the reproducibility of blood pressure variability (BPV) and spectral measures of baroreceptor sensitivity (BRS) are not well established. METHODS: We measured normal-to-normal heart beat (RR) interval and finger blood pressure (Finapres) in 14 healthy individuals on three different days. The protocol was 1 h of supine rest and 1 h of 60-degree head-up tilt. Time-series of consecutive 300-s segments as well as 1024-s segments of RR intervals and systolic, diastolic and mean blood pressures were extracted for the assessment of day-to-day and short-term reproducibility. Power spectrum analysis (Fourier) and transfer function analysis was performed. Reproducibility was assessed using the coefficient of variation (CV). The reproducibility of the mean RR interval, mean systolic, diastolic and mean blood pressure was good (CV<10 %). However, there was only moderate-to-poor reproducibility of the spectral parameters of HRV (CV range 18-36%) and BPV (16-44%) and moderate reproducibility of BRS (14-20%). CONCLUSION: Spectral estimates of BRS had only moderate reproducibility although it was better than the spectral estimates of HRV and BPV.

Beat-to-beat QT dynamics in healthy subjects.

BACKGROUND: Measures of QT dynamics express repolarization abnormalities that carry prognostic information, but the reproducibility of beat-to-beat QT dynamics has never been established. The QT interval is prolonged at night, but how the circadian rhythm and heart rate influence the dynamic QT measurements is still unsettled. The aims of the present study were: (1) to describe the reproducibility of beat-to-beat QT dynamics with respect to intrasubject, between-subject, and between-observer variability and (2) to describe the normal range, circadian variation, and heart rate dependence of QT dynamics. METHODS: Ambulatory Holter recordings were performed three times on 20 healthy volunteers and were analyzed by two experienced cardiologists. Slope and intercept of the QT/RR regression, the variability of QT and R-R intervals expressed as the standard deviation, and the relation between QT and RR variability expressed as a variability ratio were measured among other QT dynamics. RESULTS: The reproducibility of all QT dynamics was good. All QT dynamics showed circadian variation when calculated on an hourly basis. The day/night variation in slope could be explained by the differences in heart rate, whereas the day/night variation in intercept was heart rate independent. CONCLUSION: The present study shows that reliable automatic QT measurements could be performed, encouraging further evaluation of the clinical value of QT dynamics in risk stratification of cardiac patients.