Closed loop stimulation helps with weaning from chronotropic incompetence-related ventilator dependence

Journal of Interventional Cardiac Electrophysiology -     

Mechanism of repolarization change during initiation of supraventricular tachycardia

INTRODUCTION: Previous literature has documented the association between narrow QRS supraventricular tachycardia (SVT) and pronounced ST-T segment change. The aim of this study was to evaluate repolarization changes during SVT initiation and demonstrate the possible mechanism. METHODS AND RESULTS: Fifty-one consecutive patients (20 men and 31 women; mean age 46.1 +/- 16.4 years) with narrow QRS SVT (32 patients with AV nodal reentrant tachycardia and 19 patients with AV reentrant tachycardia) were included. We retrospectively analyzed the intracardiac recordings and ST-T segment changes on 12-lead surface ECGs during SVT initiation. Twenty-six (51%) patients developed ST segment repolarization changes during SVT initiation. Patients with shorter baseline sinus cycle length, shorter tachycardia cycle length, elevated systolic blood pressure before tachycardia induction, and greater reduction of systolic blood pressure had a higher incidence of repolarization changes. However, multivariate analysis showed that reduction of systolic blood pressure after SVT induction was the only independent predictor of repolarization changes. Furthermore, the maximal degree of ST segment depression during SVT correlated with the reduction of systolic blood pressure (r = 0.75, P < 0.001). CONCLUSION: Repolarization changes during SVT initiation were caused mainly by concurrent hemodynamic change after SVT initiation with abrupt cycle length shortening.     

A case report of left ventricular non-compaction in progression to dilated cardiomyopathy: Diagnostic utilization of multiple imaging modalities

Left ventricular non-compaction, which is characterized by left ventricular hypertrabeculation, is a rare congenital cardiomyopathy. The changing and progressing morphology, with different clinical manifestations, made the diagnosis difficult. Here is a case report of a middle-age woman, who had exercise intolerance for many years. Traditional echocardiography showed findings of dilated cardiomyopathy but obscure trabeculations, which was clearly seen by three-dimensional echocardiography. Subsequent cardiac magnetic resonance imaging well demonstrated the myocardial non-compaction and delayed enhancement. LVNC could be found early in a child, and also in a mid-age adult. When a patient with LVNC had progressing heart failure, the hypertrabeculation may become less prominent. The utilization of three-dimensional echocardiography and MRI would help identify such landmark findings.     

Mechanism of adenosine-induced termination of focal atrial tachycardia

INTRODUCTION: Adenosine can terminate most focal atrial tachycardias (ATs). However, information about the termination mechanism is limited. This study investigated the effects and mechanism of adenosine on terminating focal AT using a three-dimensional noncontact mapping system. METHODS AND RESULTS: The study consisted of 7 patients (4 men and 3 women; age 44 +/- 29 years) with focal AT. Cycle length variation and atrial activation pattern at baseline and just before AT termination by adenosine (3-12 mg) were analyzed. Noncontact mapping demonstrated focal AT propagated from the origin (O) with preferential conduction and spread away from the breakout sites to the whole atrium. Compared to baseline AT, termination episodes revealed higher mean beat-to-beat variation of AT cycle length (11.7 +/- 11.7 msec vs 4.7 +/- 4.5 msec, P < 0.001) and standard deviation of normalized AT cycle length (0.033 +/- 0.014 vs 0.011 +/- 0.005, P < 0.001). In termination episodes, adenosine significantly decreased the peak negative voltage of AT-O (-27.2 +/- 15.3%, P < 0.01), preferential conduction (proximal: -32.1 +/- 18.7, mid: -28.4 +/- 22.8, distal portion: -29.6 +/- 21.4%, P < 0.01), and breakout (-31.4 +/- 12.5%, P < 0.01). However, adenosine did not affect voltage in nontermination episodes. Adenosine shifted the locations of AT-O in 5 of 10 AT episodes with termination. Mean number of shifting AT-O was 2.4 +/- 1.5 (range 1-4), with maximum shifting distance of 15.0 +/- 3.1 (range 10-19) mm. Focal activation at AT-O simply disappeared in all termination episodes and therefore was not due to conduction block within preferential conduction or breakout site. Catheter ablation lesions covered 50% of total shifting origins, without late recurrence. CONCLUSION: Adenosine-induced AT termination was associated with significantly decreased electrogram voltage, shifting AT-O locations, and disappearance of focal activation.     

The utilization of carotid artery imaging beyond metabolic scores and high-sensitivity CRP in screening intermediate-to-high Framingham risk of asymptomatic Taiwanese population

To compare the diagnostic accuracy of various cardiovascular screening tools in asymptomatic subjects with intermediate-to-high risk Framingham risk score (FRS). In addition, we also investigated whether carotid artery study could further add incremental value beyond metabolic abnormality and inflammatory marker in this issue. 1,200 asymptomatic subjects who underwent health evaluation were recruited in our study. FRS was calculated in all participants based on clinical variables, body surface electrocardiography, medical histories, and life styles. Metabolic scores, serum high-sensitivity C reactive protein (hs-CRP) level and carotid artery study in assessing intima-media-thickness (CIMT) and plaque were all obtained and compared to FRS. Comparison of diagnostic accuracy was then conducted among these different tools aiming at a more efficient screen in identifying intermediate-to-high FRS. Of all, 1,101 participants (mean age 50.6 ± 10.4, 38.6 % women) were finally entered in our study after exclusion of known cardiovascular diseases. By utilizing common carotid IMT (CCIMT) equal or larger than 1 mm, best specificity (98.27, 95 % CI 97.24–98.99) was achieved in identifying intermediate-to-high FRS subject. The most optimal cut-off in identifying intermediate-to-high FRS for metabolic scores, hs-CRP and CCIMT was 2, 0.101 mg/dL and 0.65 mm, respectively. Both receiver operating characteristic curve and likelihood ratio tests showed that information provided by carotid artery study further showed significant incremental value when superimposed on metabolic scores and hs-CRP (all p < 0.05) in screening intermediate-to-high FRS subjects. Though diagnostic accuracy may differ to some degree by using different cut-off values, a low metabolic score seemed to have the best sensitivity with abnormal CCIMT yielded highest specificity in screening a subject with future cardiovascular risks. Carotid artery study added significant clinical incremental value in discriminating projected risk beyond metabolic scores and hs-CRP.     

The Relationship Among Atrium Electromechanical Interval,Insulin Resistance,and Metabolic Syndrome

Background

Metabolic syndrome (MS) is an important risk factor of atrial fibrillation. However, an understanding of the adverse effects of MS on left atrial (LA) functional assessment in terms of electromechanical interval, a convenient parameter that can reflect the process of LA remodelling, has been lacking. The goal of this study was to investigate the association between electromechanical interval and MS.

Methods

In all, 337 patients (91 with MS) with mean age of 51.9 ± 9.0 years were enrolled. Metabolic syndrome was defined by National Cholesterol Education Program–Adult Treatment Panel III score. Insulin resistance was assessed by the homeostasis model assessment–insulin resistance method. The electromechanical interval, defined as the time from initiation of P wave deflection to peak of mitral inflow Doppler A wave (PA-PDI), was measured.

Results

Patients with MS had significantly longer PA-PDI intervals compared with those of patients without MS (131.0 ± 12.4 milliseconds vs 123.2 ± 14.0 milliseconds, P < 0.001). Longer PA-PDI intervals were observed in subjects with higher metabolic scores (P < 0.05). In patients with small LA size, PA-PDI intervals, but not LA dimensions, were significantly different between groups with and without MS (P < 0.05). Additionally, PA-PDI interval was positively correlated with insulin resistance (r = 0.267, P < 0.001).

Conclusions

PA-PDI intervals were longer in patients with MS compared with those of patients without MS and tracked with insulin resistance. PA-PDI may be a useful clinical parameter to represent the degree of atrial remodelling in subjects with metabolic derangements.