No abstract available.
Defibrillators, Implantable* ; Humans ; Magnetic Resonance Imaging*

The use of both magnetic resonance imaging (MRI) and pacing devices has vastly increased worldwide in recent years. A significant number of implanted patients will likely need monitoring using magnetic resonance imaging (MRI) over the course of the lifetime of their device. Some studies have demonstrated that with appropriate precautions, MRI can be safely performed in patients with selected implantable pacemakers. However, MRI is still contraindicated in patients with pacemakers. Recently, new pacing systems have been specifically designed for safe use in the MRI environment. The first reported experience suggests that the technology is safe and may allow patients with these new pacemakers to undergo MRI. This review will describe the outstanding issues and controversies surrounding the safety of MRI in patients with pacemakers, and the potential benefits of the new MRI-conditional technology. We will also discuss how to decide whether an MRI-conditional system should be implanted, and highlight key issues that warrant further studies.
Humans ; Magnetic Resonance Imaging*

Magnetic resonance imaging (MRI) is increasingly becoming a standard of care and hence, an unmatched and irreplaceable diagnostic method. However, patients with implantable cardiac devices have not been guaranteed safety when exposed to the MRI environment. For this reason, Medtronic has taken the initiative and developed SureScan™ devices, which are MRI compatible devices for patients that would enable them to undergo MRI scans safely. The current technological developments in magnetic resonance (MR) and their clinical applications are discussed.
Cardiology ; Humans ; Magnetic Resonance Imaging* ; Methods ; Safety Management ; Standard of Care

Gaining a complete understanding of the physics of magnetic resonance imaging (MRI) is a daunting task. However, as cardiac MRI is being increasingly used in cardiovascular medicine, understanding the basics of MRI physics has become necessary for appropriate assessment of the images and correct interpretation of the findings. MRI is an imaging modality that utilizes the magnetic potential of the body. When the body is placed inside an extremely strong magnetic field, the protons of the water molecules inside the body align along the field, after which, the proton spins are exposed to a radiofrequency pulse with a frequency that matches the precession frequency of the protons in the body. This causes the precession of the protons to resonate and increase in amplitude. Simultaneously, three-dimensional magnetic gradients are applied for targeting specific slices of the body and discriminating the two-dimensional orientation of the organs; this is followed by emission of electromagnetic pulses generated by the resonance with varying frequencies and phases from various parts of the body. As soon as the input pulse has ceased, the machine starts absorbing the electromagnetic pulses that are being emitted by the body. These waves are mathematically converted into images of the internal organs and are visualized through rapid computer processing. To improve the contrast between tissues and abnormal structures, specific pulse sequences and weighting of the images are applied. This review summarizes the principles of MRI physics for clinicians who lack an understanding of fundamental physics.
Magnetic Fields ; Magnetic Resonance Imaging ; Magnets ; Protons ; Water

BACKGROUND AND OBJECTIVES: Previous studies have demonstrated an association between several single nucleotide polymorphisms and atrial fibrillation (AF). We hypothesized that the phenotypes of AF patients were associated with common AF susceptibility alleles. SUBJECTS AND METHODS: A total of 659 patients (57±9 years, 76% male) with AF who underwent catheter ablation and 659 age, and sex-matched controls were genotyped for the common AF susceptibility alleles rs2200733 and rs6843082 at 4q25, rs2106261 at ZFHX3, and rs13376333 at KCNN3. The phenotypes of AF patients, including electroanatomical characteristics of the left atrium and recurrence after ablation, were compared. RESULTS: The rs2200733 variant allele carriers have larger left atrium volume (128.5±40.7 vs. 113.5±29.2 mL, p=0.020), longer PR interval (185.9±32.6 vs. 174.8±21.9 ms, p=0.018), and higher amplitude of negative P-wave terminal force in Lead V₁ (0.07±0.04 vs. 0.05±0.04 mV, p=0.015) on electrocardiography than those without the variant allele. When the patients were assigned to three groups according to the number of variant alleles (Group A: no variant, n=15; Group B: 1 variant, n=158; Group C: 2 variants, n=439), incremental prognostic value, according to the number of variant alleles, was demonstrated (Log Rank p=0.015). Multivariate Cox regression analysis showed that persistent AF (OR 1.677, 95% CI 1.176-2.381, p=0.004) and the number of variants (OR 1.552, 95% CI 1.099-2.222, p=0.015) were independent predictors for recurrence of AF. CONCLUSION: This study showed the common AF susceptibility alleles at 4q25 and ZFHX3 are associated with electroanatomical characteristics of the left atrium and the clinical outcomes of catheter ablation in Korean patients with AF.
Alleles ; Atrial Fibrillation* ; Catheter Ablation* ; Electrocardiography ; Heart Atria* ; Humans ; Phenotype ; Polymorphism, Single Nucleotide* ; Recurrence

BACKGROUND AND OBJECTIVES: Myocardial wall stretch is the main trigger for pro-brain natriuretic peptide (pro-BNP) secretion. The reduced heart rate associated with bradyarrhythmia increases stroke volume, resulting in increased wall tension. Therefore, we propose that bradyarrhythmia could increase plasma N-terminal pro-BNP (NT-pro-BNP) levels. SUBJECTS AND METHODS: We enrolled 125 patients who received a temporary pacemaker because they had sinus node dysfunction (SND) or atrioventricular blocks (AVBs). Patients with renal dysfunction, hyperkalemia, reduced left ventricular systolic function (left ventricular ejection fraction [LVEF], <40%), and atrial fibrillation were excluded. Heart failure (HF) was defined as an NT-pro-BNP level of >300 pg/mL. We evaluated history of hypertension, diabetes mellitus, and ischemic heart disease, plasma NT-pro-BNP levels, body mass index (BMI), LVEF, left atrial diameter (LAD), and escape rhythm rate. RESULTS: The log plasma NT-pro-BNP level of the patients with AVBs was significantly increased compared to that of the patients with SND (3.17±0.55 vs. 2.93±0.64 pg/mL, respectively; p=0.03). The incidence of HF was 72.5% (106 patients; 44 male patients). Further, the incidence of HF was significantly higher among patients with AVBs than among patients with SND. The type of bradyarrhythmia was found to be the only predictor of HF after adjusting for age, history of hypertension, LAD, and LVEF. The LVEF, LAD, and ventricular rate were similar between the 2 groups. CONCLUSION: As in the case of patients with tachyarrhythmia, bradyarrhythmia may increase plasma NT-pro-BNP levels, leading to HF. Therefore, the possibility of HF should be considered in patients with bradyarrhythmia.
Arrhythmias, Cardiac ; Atrial Fibrillation ; Atrioventricular Block ; Body Mass Index ; Bradycardia* ; Diabetes Mellitus ; Heart Failure ; Heart Rate ; Humans ; Hyperkalemia ; Hypertension ; Incidence ; Male ; Myocardial Ischemia ; Plasma* ; Sick Sinus Syndrome ; Stroke Volume ; Tachycardia ; United Nations

53-year-old female was admitted to our institution with alternating atrial flutter and junctional bradycardia. The patient had undergone the Warden procedure to correct sinus venosus type atrial septal defect combined with partial anomalous pulmonary venous return, and ring tricuspid annuloplasty for severe tricuspid regurgitation. She also had persistent left superior vena cava (PLSVC). With the assistance of a 3D electroanatomic mapping system, catheter ablation therapy was used successfully to treat atrial flutter associated with a channel in the right atrial scar, and a pacemaker was implanted through the PLSVC because of resulting symptomatic bradycardia.
Atrial Flutter ; Bradycardia* ; Cardiac Surgical Procedures ; Catheter Ablation ; Cicatrix ; Female ; Heart Defects, Congenital ; Heart Septal Defects, Atrial ; Humans ; Middle Aged ; Pacemaker, Artificial ; Scimitar Syndrome ; Tachycardia* ; Tricuspid Valve Insufficiency ; Vena Cava, Superior*

The delivery of single His-refractory ventricular extra-stimulus during supraventricular tachycardia is useful to identify the mechanism of the tachycardia. We present the different responses based on the ventricular extra-stimulus site. Our findings demonstrate that the atrial activation via an accessory pathway was not advanced based on the ventricular pacing site. Therefore, atrioventricular tachycardia could masquerade as atrioventricular nodal reentrant tachycardia.
Tachycardia ; Tachycardia, Atrioventricular Nodal Reentry ; Tachycardia, Supraventricular*

We report the case of a 19-year-old male who successfully recovered from sudden cardiac arrest. Careful evaluation did not reveal any electrical or structural abnormalities. He underwent implantable cardioverter defibrillator (ICD) implantation, with a diagnosis of idiopathic ventricular fibrillation (VF). Three months later, VF recurred and was successfully terminated by ICD shock. Electrocardiogram (ECG) revealed a slurred type J point elevation at the inferolateral leads with a horizontal/descending ST segment change, which was not present during the initial hospitalization. Cilostazol was prescribed to prevent further lethal ventricular arrhythmias. Subsequently, no arrhythmic events were reported, and the J wave disappeared at the follow-up ECG. However, recurrent VF episodes with an interval of 1–2 weeks occurred 1 year later, and were terminated by ICD shock. Simultaneous ECG revealed a J point elevation at the inferolateral leads. Cilostazol was replaced by quinidine. Subsequently, no arrhythmic event recurred for over 12 months. Serial follow-up ECG is needed to identify masked inherited primary arrhythmic syndromes in sudden cardiac arrest survivors diagnosed with idiopathic VF. Cilostazol and quinidine might be good therapeutic options to prevent further lethal events in cases where the J wave syndrome is present with recurrent ventricular arrhythmias.
Anti-Arrhythmia Agents ; Arrhythmias, Cardiac ; Death, Sudden, Cardiac* ; Defibrillators ; Diagnosis ; Electrocardiography ; Follow-Up Studies ; Heart Arrest ; Hospitalization ; Humans ; Male ; Masks ; Quinidine ; Shock ; Survivors ; Ventricular Fibrillation ; Young Adult

No abstract available.
Atrial Fibrillation* ; Humans