QRS morphology in lead V1 for the rapid localization of idiopathic ventricular arrhythmias originating from the left ventricular papillary muscles: A novel electrocardiographic criterion

BACKGROUND

Twelve-lead electrocardiogram (ECG) criteria have been developed to identify idiopathic ventricular arrhythmias (VAs) from the left ventricular (LV) papillary muscles (PAPs), but accurate localization remains a challenge.

OBJECTIVE

The purpose of this study was to develop ECG criteria for accurate localization of LV PAP VAs using lead V₁ exclusively.

METHODS

Consecutive patients undergoing mapping and ablation of VAs from the LV PAPs guided by intracardiac echocardiography from 2007 to 2018 were reviewed (study group). The QRS morphology in lead V₁ was compared to patients with VAs with a "right bundle branch block" morphology from other LV locations (reference group). Patients with structural heart disease were excluded.

RESULTS

One hundred eleven patients with LV PAP VAs (mean age 54 ± 16 years; 65% men) were identified, including 64 (55%) from the posteromedial PAP and 47 (42%) from the anterolateral PAP. The reference group included patients with VAs from the following LV locations: fascicles (n = 21), outflow tract (n = 36), ostium (n = 37), inferobasal segment (n = 12), and apex (5). PAP VAs showed 3 distinct QRS morphologies in lead V₁ 93% of the time: Rr (53%), R with a slurred downslope (29%), and RR (11%). Sensitivity, specificity, positive predictive value, and negative predictive value for the 3 morphologies combined are 93%, 98%, 98%, and 93%, respectively. The intrinsicoid deflection of PAP VAs in lead V₁ was shorter than that of the reference group (63 ± 13 ms vs 79 ± 24 ms; P < .001). An intrinsicoid deflection time of <74 ms best differentiated the 2 groups (sensitivity 79%; specificity 87%).

CONCLUSION

VAs originating from the LV PAPs manifest unique QRS morphologies in lead V₁, which can aid in rapid and accurate localization.

Motor cortex is required for learning but not for executing a motor skill

Motor cortex is widely believed to underlie the acquisition and execution of motor skills, but its contributions to these processes are not fully understood. One reason is that studies on motor skills often conflate motor cortex's established role in dexterous control with roles in learning and producing task-specific motor sequences. To dissociate these aspects, we developed a motor task for rats that trains spatiotemporally precise movement patterns without requirements for dexterity. Remarkably, motor cortex lesions had no discernible effect on the acquired skills, which were expressed in their distinct pre-lesion forms on the very first day of post-lesion training. Motor cortex lesions prior to training, however, rendered rats unable to acquire the stereotyped motor sequences required for the task. These results suggest a remarkable capacity of subcortical motor circuits to execute learned skills and a previously unappreciated role for motor cortex in "tutoring" these circuits during learning.

EEG analysis reveals widespread directed functional interactions related to a painful cutaneous laser stimulus

During attention to a painful cutaneous laser stimulus, event-related causality (ERC) has been detected in recordings from subdural electrodes implanted directly over cortical modules for the treatment of epilepsy. However, these studies afforded limited sampling of modules and did not examine interactions with a nonpainful stimulus as a control. We now sample scalp EEG to test the hypothesis that attention to the laser stimulus is associated with poststimulus ERC interactions that are different from those with attention to a nonpainful stimulus. Subjects attended to (counted) either a painful laser stimulus (laser attention task) or a nonpainful electrical cutaneous stimulus that produced distraction from the laser (laser distraction task). Both of these stimuli were presented in random order in a single train. The intensities of both stimuli were adjusted to produce similar baseline salience and sensations in the same cutaneous territory. The results demonstrated that EEG channels with poststimulus ERC interactions were consistently different during the laser stimulus versus the electric stimulus. Poststimulus ERC interactions for the laser attention task were different from the laser distraction task. Furthermore, scalp EEG frontal channels play a driver role while parietal temporal channels play a receiver role during both tasks, although this does not prove that these channels are connected. Sites at which large numbers of ERC interactions were found for both laser attention and distraction tasks (critical sites) were located at Cz, Pz, and C3. Stimulation leading to disruption of sites of these pain-related interactions may produce analgesia for acute pain.

Medical student appraisal: searching on smartphones

BACKGROUND

The rapidly growing industry for mobile medical applications provides numerous smartphone resources designed for healthcare professionals. However, not all applications are equally useful in addressing the questions of early medical trainees.

METHODS

Three popular, free, mobile healthcare applications were evaluated along with a Google(TM) web search on both Apple(TM) and Android(TM) devices. Six medical students at a large academic hospital evaluated each application for a one-week period while on various clinical rotations.

RESULTS

Google(TM) was the most frequently used search method and presented multimedia resources but was inefficient for obtaining clinical management information. Epocrates(TM) Pill ID feature was praised for its clinical utility. Medscape(TM) had the highest satisfaction of search and excelled through interactive educational features. Micromedex(TM) offered both FDA and off-label dosing for drugs.

DISCUSSION

Google(TM) was the preferred search method for questions related to basic disease processes and multimedia resources, but was inadequate for clinical management. Caution should also be exercised when using Google(TM) in front of patients. Medscape(TM) was the most appealing application due to a broad scope of content and educational features relevant to medical trainees. Students should also be cognizant of how mobile technology may be perceived by their evaluators to avoid false impressions.