Factors affecting dental students' postgraduate plans: A multi-site study.

PURPOSE: This multi-site study examined dental students' postgraduate plans and factors affecting them, perceptions of pathways with the best future, and whether those postgraduate plans changed during dental school. METHODS: An online survey was made available to all four dental classes (2018, 2019, 2020, and 2021) and advanced standing/international dental students at eight US dental schools. The survey questionnaire consisted of two parts: (1) 14 questions pertaining to demographic information and (2) 11 questions pertaining to career path choices and possible influencing factors. RESULTS: Overall response rate was approximately 38.4% (1459/3800). For those responding 34.0% planned to enroll in a general dentistry residency, followed by associate dentist in a private practice (31.4%), and specialty residency (17.6%). Quality of life, to increase knowledge/clinical skills, and intellectual satisfaction were most often rated extremely important factors; Influence of family members in dentistry and prestigious specialty received the most responses of not important. General dentistry was perceived to have the best future in terms of overall impact on the profession, potential for positive impact on patient's quality of life, and personal quality of life; oral and maxillofacial surgery was believed to have the best future in terms of salary. Students changed their postgraduate plan during dental school 43.0% of the time, with race (p = 0.006) and year of progress toward degree (p < 0.001) being significant associations. CONCLUSIONS: General dentistry remains the most popular pathway. Many dental students change their plans during dental school; a better understanding of these trends and contributing factors may aid development of practice readiness curricula.

Evaluation of a real-time magnetic resonance imaging-guided electrophysiology system for structural and electrophysiological ventricular tachycardia substrate assessment.

AIMS: Potential advantages of real-time magnetic resonance imaging (MRI)-guided electrophysiology (MR-EP) include contemporaneous three-dimensional substrate assessment at the time of intervention, improved procedural guidance, and ablation lesion assessment. We evaluated a novel real-time MR-EP system to perform endocardial voltage mapping and assessment of delayed conduction in a porcine ischaemia-reperfusion model. METHODS AND RESULTS: Sites of low voltage and slow conduction identified using the system were registered and compared to regions of late gadolinium enhancement (LGE) on MRI. The Sorensen-Dice similarity coefficient (DSC) between LGE scar maps and voltage maps was computed on a nodal basis. A total of 445 electrograms were recorded in sinus rhythm (range: 30-186) using the MR-EP system including 138 electrograms from LGE regions. Pacing captured at 103 sites; 47 (45.6%) sites had a stimulus-to-QRS (S-QRS) delay of ≥40 ms. Using conventional (0.5-1.5 mV) bipolar voltage thresholds, the sensitivity and specificity of voltage mapping using the MR-EP system to identify MR-derived LGE was 57% and 96%, respectively. Voltage mapping had a better predictive ability in detecting LGE compared to S-QRS measurements using this system (area under curve: 0.907 vs. 0.840). Using an electrical threshold of 1.5 mV to define abnormal myocardium, the total DSC, scar DSC, and normal myocardium DSC between voltage maps and LGE scar maps was 79.0 ± 6.0%, 35.0 ± 10.1%, and 90.4 ± 8.6%, respectively. CONCLUSION: Low-voltage zones and regions of delayed conduction determined using a real-time MR-EP system are moderately associated with LGE areas identified on MRI.

Local activation time sampling density for atrial tachycardia contact mapping: how much is enough?

Aims: Local activation time (LAT) mapping forms the cornerstone of atrial tachycardia diagnosis. Although anatomic and positional accuracy of electroanatomic mapping (EAM) systems have been validated, the effect of electrode sampling density on LAT map reconstruction is not known. Here, we study the effect of chamber geometry and activation complexity on optimal LAT sampling density using a combined in silico and in vivo approach. Methods and results: In vivo 21 atrial tachycardia maps were studied in three groups: (1) focal activation, (2) macro-re-entry, and (3) localized re-entry. In silico activation was simulated on a 4×4cm atrial monolayer, sampled randomly at 0.25-10 points/cm2 and used to re-interpolate LAT maps. Activation patterns were studied in the geometrically simple porcine right atrium (RA) and complex human left atrium (LA). Activation complexity was introduced into the porcine RA by incomplete inter-caval linear ablation. In all cases, optimal sampling density was defined as the highest density resulting in minimal further error reduction in the re-interpolated maps. Optimal sampling densities for LA tachycardias were 0.67 ± 0.17 points/cm2 (focal activation), 1.05 ± 0.32 points/cm2 (macro-re-entry) and 1.23 ± 0.26 points/cm2 (localized re-entry), P = 0.0031. Increasing activation complexity was associated with increased optimal sampling density both in silico (focal activation 1.09 ± 0.14 points/cm2; re-entry 1.44 ± 0.49 points/cm2; spiral-wave 1.50 ± 0.34 points/cm2, P < 0.0001) and in vivo (porcine RA pre-ablation 0.45 ± 0.13 vs. post-ablation 0.78 ± 0.17 points/cm2, P = 0.0008). Increasing chamber geometry was also associated with increased optimal sampling density (0.61 ± 0.22 points/cm2 vs. 1.0 ± 0.34 points/cm2, P = 0.0015). Conclusion: Optimal sampling densities can be identified to maximize diagnostic yield of LAT maps. Greater sampling density is required to correctly reveal complex activation and represent activation across complex geometries. Overall, the optimal sampling density for LAT map interpolation defined in this study was ∼1.0-1.5 points/cm2.

Cardiac Electrophysiology Under MRI Guidance: an Emerging Technology.

MR-guidance of electrophysiological (EP) procedures offers the potential for enhanced arrhythmia substrate assessment, improved procedural guidance and real-time assessment of ablation lesion formation. Accurate device tracking techniques, using both active and passive methods, have been developed to offer an interface similar to electroanatomic mapping platforms, and MR-compatible EP equipment continues to be developed. Progress to clinical implementation of these technically complex fields has been relatively slow over the last 10 years, but recent developments have led to successful clinical experience. However, further advances, particularly in harnessing the full imaging potential of CMR, are required to realise the mainstream adoption of this powerful guidance modality.

Antibiotic prophylaxis for infective endocarditis: a systematic review and meta-analysis.

OBJECTIVE: The use of antibiotic prophylaxis (AP) for prevention of infective endocarditis (IE) is controversial. In recent years, guidelines to cardiologists and dentists have advised restriction of AP to high-risk groups (in Europe and the USA) or against its use at all (in the UK). The objective of this systematic review was to appraise the evidence for use of AP for prevention of bacteraemia or IE in patients undergoing dental procedures. METHODS: We conducted electronic searches in Medline, Embase, Cochrane Library and ISI Web of Science. We assessed the methodological characteristics of included studies using the Strengthening the Reporting of Observational Studies in Epidemiology criteria for observational studies and the Cochrane Risk of Bias Tool for trials. Two reviewers independently determined the eligibility of studies, assessed the methodology of included studies and extracted the data. RESULTS: We identified 178 eligible studies, of which 36 were included in the review. This included 10 time-trend studies, 5 observational studies and 21 trials. All trials identified used bacteraemia as an endpoint rather than IE. One time-trend study suggests that total AP restriction may be associated with a rising incidence of IE, while data on the consequences of relative AP restriction are conflicting. Meta-analysis of trials indicates that AP is effective in reducing the incidence of bacteraemia (risk ratio 0.53, 95% CI 0.49 to 0.57, p<0.01), but case-control studies suggest this may not translate to a statistically significant protective effect against IE in patients at low risk of disease. CONCLUSIONS: The evidence base for the use of AP is limited, heterogeneous and the methodological quality of many studies is poor. Postprocedural bacteraemia is not a good surrogate endpoint for IE. Given the logistical challenges of a randomised trial, high-quality case-control studies would help to evaluate the role of dental procedures in causing IE and the efficacy of AP in its prevention.

Development, Preclinical Validation, and Clinical Translation of a Cardiac Magnetic Resonance - Electrophysiology System With Active Catheter Tracking for Ablation of Cardiac Arrhythmia.

OBJECTIVES: This study sought to develop an actively tracked cardiac magnetic resonance-guided electrophysiology (CMR-EP) system and perform first-in-human clinical ablation procedures. BACKGROUND: CMR-EP offers high-resolution anatomy, arrhythmia substrate, and ablation lesion visualization in the absence of ionizing radiation. Implementation of active tracking, where catheter position is continuously transmitted in a manner analogous to electroanatomic mapping (EAM), is crucial for CMR-EP to take the step from theoretical technology to practical clinical tool. METHODS: The setup integrated a clinical 1.5-T scanner, an EP recording and ablation system, and a real-time image guidance platform with components undergoing ex vivo validation. The full system was assessed using a preclinical study (5 pigs), including mapping and ablation with histological validation. For the clinical study, 10 human subjects with typical atrial flutter (age 62 ± 15 years) underwent MR-guided cavotricuspid isthmus (CTI) ablation. RESULTS: The components of the CMR-EP system were safe (magnetically induced torque, radiofrequency heating) and effective in the CMR environment (location precision). Targeted radiofrequency ablation was performed in all animals and 9 (90%) humans. Seven patients had CTI ablation completed using CMR guidance alone; 2 patients required completion under fluoroscopy, with 2 late flutter recurrences. Acute and chronic CMR imaging demonstrated efficacious lesion formation, verified with histology in animals. Anatomic shape of the CTI was an independent predictor of procedural success. CONCLUSIONS: CMR-EP using active catheter tracking is safe and feasible. The CMR-EP setup provides an effective workflow and has the potential to change the way in which ablation procedures may be performed.

Repeat left atrial catheter ablation: cardiac magnetic resonance prediction of endocardial voltage and gaps in ablation lesion sets.

BACKGROUND: Studies have reported an inverse relationship between late gadolinium enhancement (LGE) cardiac magnetic resonance (CMR) signal intensity and left atrial (LA) endocardial voltage after LA ablation. However, there is controversy regarding the reproducibility of atrial LGE CMR and its ability to identify gaps in ablation lesions. Using systematic and objective techniques, this study examines the correlation between atrial CMR and endocardial voltage. METHODS AND RESULTS: Twenty patients who had previous ablation for atrial fibrillation and represented with paroxysmal atrial fibrillation or atrial tachycardia underwent preablation LGE CMR. During the ablation procedure, high-density point-by-point Carto voltage maps were acquired. Three-dimensional CMR reconstructions were registered with the Carto anatomies to allow comparison of voltage and LGE signal intensity. Signal intensities around the left and right pulmonary vein antra and along the LA roof and mitral lines on the CMR-segmented LA shells were extracted to examine differences between electrically isolated and reconnected lesions. There were a total of 6767 data points across the 20 patients. Only 119 (1.8%) of the points were ≤ 0.05 mV. There was only a weak inverse correlation between either unipolar (r = -0.18) or bipolar (r = -0.17) voltage and LGE CMR signal intensities with low voltage occurring across a large range of signal intensities. Signal intensities were not statistically different for electrically isolated and reconnected lesions. CONCLUSIONS: This study demonstrates that there is only a weak point-by-point relationship between LGE CMR and endocardial voltage in patients undergoing repeat LA ablation. Using an objective method of assessing gaps in ablation lesions, LGE CMR is unable to reliably predict sites of electrical conduction.

Vascular and extravascular findings on magnetic resonance angiography of the thoracic aorta and the origin of the great vessels.

PURPOSE: To investigate the presence of relevant vascular and incidental extravascular findings in patients undergoing magnetic resonance angiography (MRA) of the thoracic aorta and origin of the great vessels. MATERIALS AND METHODS: In all, 165 consecutive patients (mean age 61 ± 12 years) underwent 1.5 T MRA of the thorax. Two researchers identified vascular and incidental extravascular findings. Clinically relevant vascular findings were defined. Extravascular findings were categorized as minor (Group A, without change in patient treatment), intermediate (Group B, unclear clinical relevance, requiring additional investigations), and major (Group C, causing a change in patient treatment). RESULTS: A total of 306 relevant vascular findings were found in our cohort. A total of 397 extravascular findings were observed among the patients and were classified as Group A findings in 81.9% (325/397 findings, observed in 146 of 165 patients), as Group B findings in 15.4% (61/397 findings, observed in 52 of 165 patients), and as Group C in 2.8% of findings (11/397). The clinically relevant Group C findings were observed in 6.7% of patients (11/165), comprising eight previously unknown neoplasms (4.8% of 165), two patients with hemodynamically relevant pericardial effusion (1.2% of 165), and one patient with spondylodiscitis (0.6% of 165) detected by MRA. CONCLUSION: Relevant vascular and extravascular findings were found in patients referred for thoracic MRA. Most extravascular findings can be categorized by MRA as minor, while others required further diagnostics since they may be malignant or otherwise clinically relevant.

Quantitative assessment of the effects of therapeutic hypothermia on early repolarization in idiopathic ventricular fibrillation survivors: a 7-year cohort study.

BACKGROUND: The early repolarization (ER) pattern on ECG is associated with an increased risk of idiopathic ventricular fibrillation (ID-VF). Hypothermia is known to result in similar electrocardiographic changes. In this retrospective cohort study, we examine the impact of therapeutic hypothermia on ER in survivors of cardiac arrest attributed to ID-VF and draw comparisons with a control group who experienced coronary artery disease-related VF (CAD-VF). METHODS AND RESULTS: All patients who had cardiac arrest and were treated with therapeutic hypothermia over a 7-year period were considered for inclusion in the study. Forty-three patients were identified with ID-VF or CAD-VF arrest. ECGs were obtained during cooling and again after rewarming. ECGs were digitized and assessed for the presence of ER by 2 independent observers. Cooling significantly increased the prevalence (74% during cooling versus 51% at baseline temperature; P=0.044) and mean amplitude (0.78±0.10 mV during cooling versus 0.56±0.09 mV at baseline temperature; P=0.038) of ER in the overall cohort. During cooling, ER was more common among survivors of ID-VF than of CAD-VF (100% versus 67%; P=0.043). ER magnitude was significantly greater among ID-VF survivors than CAD-VF survivors both during cooling (1.16±0.18 versus 0.70±0.11 mV; P=0.044) and at baseline temperature (1.02±0.21 versus 0.42±0.09 mV; P=0.005). CONCLUSIONS: Hypothermia increases both the prevalence and magnitude of ER in cardiac arrest survivors. Despite the association of ER with ID-VF, therapeutic hypothermia only increases ER amplitude in CAD-VF survivors.

Cardiac magnetic resonance and electroanatomical mapping of acute and chronic atrial ablation injury: a histological validation study.

AIMS: To provide a comprehensive histopathological validation of cardiac magnetic resonance (CMR) and endocardial voltage mapping of acute and chronic atrial ablation injury. METHODS AND RESULTS: 16 pigs underwent pre-ablation T2-weighted (T2W) and late gadolinium enhancement (LGE) CMR and high-density voltage mapping of the right atrium (RA) and both were repeated after intercaval linear radiofrequency ablation. Eight pigs were sacrificed following the procedure for pathological examination. A further eight pigs were recovered for 8 weeks, before chronic CMR, repeat RA voltage mapping and pathological examination. Signal intensity (SI) thresholds from 0 to 15 SD above a reference SI were used to segment the RA in CMR images and segmentations compared with real lesion volumes. The SI thresholds that best approximated histological volumes were 2.3 SD for LGE post-ablation, 14.5 SD for T2W post-ablation and 3.3 SD for LGE chronically. T2-weighted chronically always underestimated lesion volume. Acute histology showed transmural injury with coagulative necrosis. Chronic histology showed transmural fibrous scar. The mean voltage at the centre of the ablation line was 3.3 mV pre-ablation, 0.6 mV immediately post-ablation, and 0.3 mV chronically. CONCLUSION: This study presents the first histopathological validation of CMR and endocardial voltage mapping to define acute and chronic atrial ablation injury, including SI thresholds that best match histological lesion volumes. An understanding of these thresholds may allow a more informed assessment of the underlying atrial substrate immediately after ablation and before repeat catheter ablation for atrial arrhythmias.

Pulmonary vein anatomy predicts freedom from atrial fibrillation using remote magnetic navigation for circumferential pulmonary vein ablation.

AIMS: Multidetector computed tomography (MDCT) is frequently used to guide circumferential pulmonary vein ablation (PVA) for treatment of atrial fibrillation (AF) as it offers accurate visualization of the left atrial (LA) and pulmonary vein (PV) anatomy. This study aimed to identify if PV anatomy is associated with outcomes following PVA using remote magnetic navigation (RMN). METHODS AND RESULTS: We analysed data from 138 consecutive patients and 146 ablation procedures referred for PVA due to drug-refractory symptomatic AF (age 63 ± 11 years; 57% men; 69% paroxysmal AF). The RMN using the stereotaxis system and open-irrigated 3.5 mm ablation catheters was used in all procedures. Prior to PVA, all patients underwent electrocardiogram-gated 64-MDCT for assessment of LA dimensions, PV anatomy, and electro-anatomical image integration during the procedure. Regular PV anatomy was found in 68%, a common left PV ostium was detected in 26%, and variant anatomy of the right PVs was detected in 6%. After a mean follow-up of 337 ± 102 days, 63% of the patients maintained sinus rhythm after the initial ablation, and 83% when including repeat PVA. Although acutely successful PV isolation did not differ between anatomical subgroups (regular 3.5 ± 0.8 vs. variant 3.2 ± 1.3; P = 0.31), AF recurrence was significantly higher in patients with non-regular PV anatomy (P = 0.04, hazard ratio 1.72). Pulmonary vein anatomy did not influence complication rates. CONCLUSION: Pulmonary vein anatomy assessed by MDCT is a good predictor of AF recurrence after PVA using RMN.

Left ventricular filling and diastolic myocardial deformation in chronic primary mitral regurgitation.

AIMS: Chronic primary mitral regurgitation (MR) results in enhanced filling of the left ventricle (LV) during early diastole. Filling is impaired with the onset of LV systolic dysfunction, due to increased myocardial stiffness and reduced restoring forces. We investigated echocardiographic parameters of early diastolic function in relation to LV systolic function. METHODS AND RESULTS: Early diastolic transmitral flow and tissue Doppler velocities, propagation velocity of early filling (V(p)), and early diastolic strain rates (SR-E) were measured in 30 patients with chronic degenerative MR and 30 age-matched controls. MR subjects were further subdivided into group 1 (14 subjects) if they had well compensated LV, and group 2 (16 subjects) if they had one or more of the following: functional limitation (> NYHA class I), LV end-systolic diameter >or=4.0 cm, and LV ejection fraction