Changes in QT Interval during Exercise Testing in Patients with VVI Pacemakers

. The changes in QT intervals were studied in nine patients with normal sinus node function who had VVI pacemakers. Though PP intervals uniformly shortened during exercise, the change in QaT* intervals during exercise was variable. The correlation between PP and QaT intervals varied from case to case. A good correlation was found in only two cases (r =+0.816 or +0.897); a fair correlation was found in four cases (r =+0.672, +0.615, +0.615, or −0.669) and in the remaining three, the correlation was poor (r =+0.494, +0.467 or−0.424). In patients who are candidates for VTI pacemaker implantation, changes in QaT intervals should be assessed during exercise stress testing to determine if the intervals shorten during exercise or not.
(QaT*: Interval from the pacing spike to the apex of T-wave.)     

Central venous pressure and shock index predict lack of hemodynamic response to volume expansion in septic shock: A prospective,observational study

Purpose

Volume expansion is a common therapeutic intervention in septic shock, although patient response to the intervention is difficult to predict. Central venous pressure (CVP) and shock index have been used independently to guide volume expansion, although their use is questionable. We hypothesize that a combination of these measurements will be useful.

Methods

In a prospective, observational study, patients with early septic shock received 10-mL/kg volume expansion at their treating physician's discretion after brief initial resuscitation in the emergency department. Central venous pressure and shock index were measured before volume expansion interventions. Cardiac index was measured immediately before and after the volume expansion using transthoracic echocardiography. Hemodynamic response was defined as an increase in a cardiac index of 15% or greater.

Results

Thirty-four volume expansions were observed in 25 patients. A CVP of 8 mm Hg or greater and a shock index of 1 beat min^− 1 mm Hg^− 1 or less individually had a good negative predictive value (83% and 88%, respectively). Of 34 volume expansions, the combination of both a high CVP and a low shock index was extremely unlikely to elicit hemodynamic response (negative predictive value, 93%; P = .02).

Conclusions

Volume expansion in patients with early septic shock with a CVP of 8 mm Hg or greater and a shock index of 1 beat min^− 1 mm Hg^− 1 or less is unlikely to lead to an increase in cardiac index.     

Echocardiography predicts closure of patent ductus arteriosus in response to ibuprofen in infants less than 28 week gestational age

Background

Patent ductus arteriosus (PDA) is a frequent problem in preterm infants, and its incidence is inversely correlated with gestational age. The efficacy of medical treatment decreases with decreasing gestational age (GA), and failure rates as well as ductus ligation rates of 40% have been reported in < 28 week GA newborns. The aim of this study was to determine whether echocardiographic parameters can predict response to ibuprofen treatment of PDA.

Study design

In a longitudinal study, 29 infants born < 28 week GA were screened for a significant PDA (left atrial to aortic root ratio > 1.4, anterior cerebral artery resistance index > 0.8, and oxygen requirement > 35%) at 24-72 h of life and, if a PDA was found, treated with 10-5-5 mg/kg ibuprofen intravenously every 24 h. Ductal parameters were monitored by serial echocardiography. Infant neurodevelopmental outcomes were assessed at 24 month corrected age.

Results

All 15 infants with significant PDA responded to the ibuprofen loading dose indicated by reduced PDA diameters or increased PDA maximum flow velocities (PDA V_max), and 7 patients showed an ongoing response resulting in a closed PDA after the 1st cycle (47%). Of the 8 non-responders, 7 received a 2nd cycle with 2 further responders (29%). All non-responders to the 2nd course had a PDA V_max ≤ 180 cm/s and increasing ductal diameters after the 3rd ibuprofen dose of the 1st course.

Conclusion

Maximum flow velocity and diameter of the PDA at the end of the 1st cycle discriminate between responders and non-responders to further ibuprofen treatment.     

Comprehensive Echocardiographic Assessment of Normal Transcatheter Valve Function

Objectives

This study aims to establish parameters for identifying normal function for each of the 3 iterations of balloon-expandable valves and 2 iterations of self-expanding valves.

Improved coronary artery blood flow following the correction of systolic dyssynchrony with cardiac resynchronization therapy

Background

Coronary blood flow (CBF) is improved by cardiac resynchronization therapy (CRT) and impaired by right ventricular apical (RVA) pacing in patients with heart failure. However, the underlying mechanism remains unclear.

Methods

Twenty-nine non-ischemic heart failure patients who responded to CRT underwent transthoracic echocardiography examination including both left anterior descending (LAD) CBF and tissue Doppler imaging in 3 pacing modes: intrinsic conduction, RVA pacing and biventricular (BiV) pacing. LAD velocity-temporal integral (LAD-VTI) and duration were measured. Systolic dyssynchrony was assessed with the standard deviation of a 12-left ventricular segmental model (Ts-SD).

Results

BiV pacing improved while RVA pacing reduced CBF compared to intrinsic conduction (all p < 0.05). Both Ts-SD and ventricular septal velocity deteriorated during RVA pacing but improved during BiV pacing (all p < 0.05). When systolic dyssynchrony was induced, lower LAD-VTI (9.5 ± 3.4 versus 12.7 ± 5.1 cm, p = 0.001) and shorter LAD diastolic duration (483 ± 92 versus 542 ± 106 ms, p = 0.010) were detected than synchronous status. Systolic dyssynchrony was inversely related to septal velocity (r = − 0.41), p<0.001 and LAD-VTI (r = − 0.30, p = 0.007), with the latter found to be moderately correlated to septal velocity (r = 0.30, p = 0.007).

Conclusion

Regional LAD flow was improved in patients subjected to BiV but worsened in those treated with RVA pacing in non-ischemic heart failure CRT responders. Systolic dyssynchrony was more commonly observed in patients subjected to RVA pacing. Reduction of septal velocity with dyssynchrony may directly lead to reduced LAD flow. Improvement of septal velocity by CRT and hence LAD flow may be an important mechanism in determining the response to CRT.