Classical response of antidromic atriofascicular tachycardia to premature atrial extrastimulus delivered during septal refractoriness

A 23‐year‐old gentleman presented with a history of palpitations. The 12‐lead electrocardiogram showed no manifest ventricular pre‐excitation. Echocardiogram was within normal limits. A retrograde study showed concentric activation of the atrium with decremental conduction. Atrial pacing from right atrial free wall showed progressive pre‐excitation. No anterograde nodal duality was documented.     

Response of narrow QRS tachycardia in a patient with surgical closure of atrial septal defect to atrial overdrive pacing: What is the mechanism?

A 57‐year old woman who had pericardial patch closure of ostium secundum atrial septal defect (ASD) at the age of 23 years presented with shortness of breath. Her echocardiogram showed no residual ASD, good biventricular function and normal pulmonary artery pressures.     

Nontransgenic models of breast cancer

Numerous models have been developed to address key elements in the biology of breast cancer development and progression. No model is ideal, but the most useful are those that reflect the natural history and histopathology of human disease, and allow for basic investigations into underlying cellular and molecular mechanisms. We describe two types of models: those that are directed toward early events in breast cancer development (hyperplastic alveolar nodules [HAN] murine model, MCF10AT human xenograft model); and those that seek to reflect the spectrum of metastatic disease (murine sister cell lines 67, 168, 4T07, 4T1). Collectively, these models provide cell lines that represent all of the sequential stages of progression in breast disease, which can be modified to test the effect of genetic changes.