Different Characteristics between Patients with Apical and Non-Apical Subtypes of Stress-Induced Cardiomyopathy

BACKGROUND: Stress-induced cardiomyopathy (SCM) is characterized by apical ballooning on echocardiography, but some of SCM patients show non-apical involvement and their characteristics are not well defined. METHODS: We investigated 56 patients that were diagnosed as SCM and divided them into 2 groups: apical ballooning syndrome (ABS, n = 49, 87.5%) and non-apical ballooning syndrome (N-ABS, n = 7, 12.5%) groups. Patients with N-ABS were significantly younger than those of the ABS group (52 +/- 11 vs. 73 +/- 10 years, p < 0.001). RESULTS: Types of preceding stressors and clinical presentation including chest pain, pulmonary edema, cardiogenic shock and in-hospital mortality were comparable between the two groups. In the N-ABS group, wall motion score index was significantly lower than in the ABS group (1.61 +/- 0.35 vs. 1.93 +/- 0.31, p = 0.016). On electrocardiogram (ECG), T-wave inversion (57.1% vs. 95.8%, p < 0.001) were less frequent in the N-ABS than in the ABS group. Furthermore, maximum QT and corrected QT (QTc) intervals in the N-ABS patients were significantly shorter than the ABS patients (QT, 419.9 +/- 66.1 vs. 487.3 +/- 79.6 ms, p = 0.038; QTc, 479.0 +/- 61.9 vs. 568.0 +/- 50.5 ms, p < 0.001). CONCLUSION: Patients with the N-ABS showed not only atypical echocardiographic findings, but also atypical clinical and ECG manifestations. Integrated consideration is needed to reach a diagnosis of the non-apical subtype of SCM.

Electrophysiological Characteristics of Arterially-Perfused Canine Pulmonary Veins: Role of the Delayed Afterdepolarization-Induced Triggered Activity

BACKGROUND AND OBJECTIVES: The mechanism responsible for the generation of ectopic beats in pulmonary veins (PVs) remains to be well defined. The present study examines the electrophysiological characteristics of the PVs and other regions of the canine left atrium (LA) under low dose (300 micrometer) caffeine condition. MATERIALS AND METHODS: Transmembrane action potentials were recorded from the left superior PVs, PV-LA junctions (PLJ, atrium <5 mm from the PV ostium), LA appendage (LAA) or Bachmann's bundle (BB) in arterially perfused canine LA-PV preparations, using floating glass microelectrodes. Rapid atrial pacing (cycle lengths 140-300 ms, 10 sec) was used to induce delayed afterdepolarizations (DAD) at the baseline and under low dose (300 micrometer) caffeine conditions. RESULTS: Spontaneous diastolic depolarization or triggered activity (TA) was not observed in any of the recording area under the baseline condition. DAD and TA were induced by caffeine in 4/8 PVs and in 3/8 PLJs, but in no LAA (0/6) or BB (0/5). These TA and DAD were also observed after termination of pacing-induced atrial tachyarrhythmia. DAD was abolished by pretreatment of the atria with verapamil or propranolol (1.0 micrometer). CONCLUSION: Spontaneous diastolic depolarization was not present in perfused canine left atria or proximal PV. Pulmonary veins and adjacent areas displayed an increased susceptibility to develop DAD-induced TA under low dose caffeine condition. This distinctive electrophysiological property of the PV and PLJ area may contribute to the arrhythmogenic substrate responsible for the ectopic activity that initiates atrial fibrillation.