Experimental Validation of Noninvasive Epicardial and Endocardial Activation Imaging.

Background: Noninvasive imaging of cardiac activation before ablation of the arrhythmogenic substrate can reduce electrophysiological procedure duration and help choosing between an endocardial or epicardial approach. A noninvasive imaging technique was evaluated that estimates both endocardial and epicardial activation from body surface potential maps. We performed a study in isolated and in situ pig hearts, estimating activation from body surface potential maps during sinus rhythm and localizing endocardial and epicardial stimulation sites.

Sublingual microvascular perfusion is altered during normobaric and hyperbaric hyperoxia.

Hyperoxia and hyperbaric oxygen therapy can restore oxygen tensions in tissues distressed by ischemic injury and poor vascularization and is believed to also yield angiogenesis and regulate tissue perfusion. The aim of this study was to develop a model in which hyperoxia-driven microvascular changes could be quantified and to test the hypothesis that microcirculatory responses to both normobaric (NB) and hyperbaric (HB) hyperoxic maneuvers are reversible. Sublingual mucosa microcirculation vessel density, proportion of perfused vessels, vessel diameters, microvascular flow index, macrohemodynamic, and blood gas parameters were examined in male rabbits breathing sequential O2/air mixtures of 21%, 55%, 100%, and return to 21% during NB (1.

Synchronization of repolarization by mechano-electrical coupling in the porcine heart.

Aims: The aim of this study was to evaluate the effect of increase in left ventricular (LV) pressure on repolarization and activation-recovery intervals.

Methods And Results: Six pig hearts were Langendorff-perfused. A compliant liquid-filled balloon, connected with a pressure transducer, inserted through the mitral orifice, could be filled until the required LV systolic pressure was obtained.

Electrocardiographic T wave and its relation with ventricular repolarization along major anatomical axes.

Background: The genesis of the electrocardiographic T wave is incompletely understood and subject to controversy. We have correlated the ventricular repolarization sequence with simultaneously recorded T waves.

Methods And Results: Nine pig hearts were Langendorff-perfused (atrial pacing, cycle length 650 ms).

Transmural dispersion of refractoriness and conduction velocity is associated with heterogeneously reduced connexin43 in a rabbit model of heart failure.

Background: Heterogeneity of repolarization and conduction is a potential source of arrhythmogenesis. In heart failure (HF), intercellular coupling is reduced and heterogeneities may become evident because of reduced intercellular coupling.

Objective: This study sought to investigate connexin43 (Cx43) expression, conduction velocity (CV), refractoriness and inducibility of arrhythmias at multiple sites of the left ventricle during HF.

Acute administration of fish oil inhibits triggered activity in isolated myocytes from rabbits and patients with heart failure.

Background: Fish oil reduces sudden death in patients with prior myocardial infarction. Sudden death in heart failure may be due to triggered activity based on disturbed calcium handling. We hypothesized that superfusion with omega3-polyunsaturated fatty acids (omega3-PUFAs) from fish inhibits triggered activity in heart failure.

Overlap syndrome of cardiac sodium channel disease in mice carrying the equivalent mutation of human SCN5A-1795insD.

Background: Patients carrying the cardiac sodium channel (SCN5A) mutation 1795insD show sudden nocturnal death and signs of multiple arrhythmia syndromes including bradycardia, conduction delay, QT prolongation, and right precordial ST-elevation. We investigated the electrophysiological characteristics of a transgenic model of the murine equivalent mutation 1798insD.

Methods And Results: On 24-hour continuous telemetry and surface ECG recordings, Scn5a(1798insD/+) heterozygous mice showed significantly lower heart rates, more bradycardic episodes (pauses > or = 500 ms), and increased PQ interval, QRS duration, and QTc interval compared with wild-type mice.

Dietary n-3 fatty acids promote arrhythmias during acute regional myocardial ischemia in isolated pig hearts.

Objective: Dietary supplementation with fish oil-derived n-3 fatty acids reduces mortality in patients with myocardial infarction, but may have adverse effects in angina patients. The underlying electrophysiologic mechanisms are poorly understood. We studied the arrhythmias and the electrophysiologic changes during regional ischemia in hearts from pigs fed a diet rich in fish oil.

Monophasic action potentials and activation recovery intervals as measures of ventricular action potential duration: experimental evidence to resolve some controversies.

Background: Activation recovery intervals (ARIs) and monophasic action potential (MAP) duration are used as measures of action potential duration in beating hearts. However, controversies exist concerning the correct way to record MAPs or calculate ARIs. We have addressed these issues experimentally.

Larger cell size in rabbits with heart failure increases myocardial conduction velocity and QRS duration.

Background: Patients with heart failure (HF) have an increased QRS duration, usually attributed to decreased conduction velocity (CV) due to ionic remodeling but which may alternatively result from increased heart size or cellular uncoupling. We investigated the relationship between QRS width, heart size, intercellular coupling, and CV in a rabbit model of moderate HF and in computer simulations.

Methods And Results: HF was induced by pressure-volume overload.

Impaired neuronal and vascular responses to angiotensin II in a rabbit congestive heart failure model.

Congestive heart failure (CHF) is characterised by activation of the renin-angiotensin-aldosterone system (RAAS) and the sympathetic nervous system (SNS). Both systems are known to interact and to potentiate each other s activities. We recently demonstrated that angiotensin II (Ang II) enhances sympathetic nerve traffic via prejunctionally-located AT1-receptors.

Conduction slowing by the gap junctional uncoupler carbenoxolone.

Background: Cellular electrical coupling is essential for normal propagation of the cardiac action potential, whereas reduced electrical coupling is associated with arrhythmias. Known cellular uncoupling agents have severe side effects on membrane ionic currents. We investigated the effect of carbenoxolone on cellular electrical coupling, membrane ionic currents, and atrial and ventricular conduction.

SR calcium handling and calcium after-transients in a rabbit model of heart failure.

Objective: After-depolarization associated arrhythmias are frequently observed in heart failure and associated with spontaneous calcium release from sarcoplasmic reticulum (SR), calcium after-transients. We hypothesize that disturbed SR calcium handling underlies calcium after-transients in heart failure (HF).

Methods: We measured the stimulation rate dependence (0.

Decreased facilitation by angiotensin II of noradrenergic neurotransmission in isolated mesenteric artery of rabbits with chronic heart failure.

Both in human and in experimental heart failure (HF), the renin-angiotensin system and the sympathetic nervous system are activated. In a previous study a facilitatory action of angiotensin II (Ang II) was shown in the rabbit mesenteric artery, which was mediated via prejunctionally located Ang II type 1 (AT ) receptors. Very little is known about the effects of Ang II on sympathetic neurotransmission at the peripheral level in congestive heart failure (CFH).