IBHRE Exam Questions and Answers 2024 Graded A

Name three causes of atrial standstill Myocardial Infarction Digitalis glycosides Hyperkalemia A 59 yo female with ischemic cardiomyopathy presents with palpitations, lightheadedness, insomnia and feels jittery. She has a CRT-D device. Takes Furosemide, potassium, lisinopril, carvedilol and amiodarone. Seeing short runs of VT on her device interrogation. Hyperthyroidism What would be your best next step for ordering tests? Thyroid panel Which antiarrhythmic drug is least likely to increase defibrillation thresholds? Sotalol is least likely to increase defibrillation thresholds and may in fact decrease it. In contrast all other drugs mentioned are likely to INCREASE defibrillation thresholds, which is why DFT testing is sometimes performed on patients newly started on other drugs (Flecainide, Verapamil, Amiodarone, Mexiletine). Two max shocks fail to terminate VF from ICD. Patient rescued externally. What would the next steps be? Reprogram shock waveform and / or shock vector. If this fails implantation of a subcutaneous shock coil is very likely to be successful but requires an invasive procedure. Repositioning of the RV lead rarely helps (unless the lead is in the RV inflow tract and can be placed far out into the RV apex). Implantation on the right side is unlikely to solve the problem as right sided implantations generally have a higher DFT. Amiodarone is likely to further increase DFT and should therefore be avoided in this patient. What does the noise on atrial channel signal? Lead noise during exercise is suggestive for a problem with the atrial lead. When looking closely at the X-ray image, an insulation defect can be detected on two of the three leads. One defect is found on the abandoned atrial lead and the second on the active atrial lead. These findings together with low lead impedance, make diagnosis of atrial lead insulation damage the most likely explanation. Atrial lead conductor problems could also result in atrial noise but impedance would be expected to increase in this situation. There is no indication of a ventricular lead problem. Myopotential oversensing in the context of a unipolar atrial electrode is possible but would not explain the X ray findings and low atrial lead impedance. What is A00 pacing mode? A00 mode in itself causes undersensing. MADIT RIT trial MADIT RIT programming devices implanted for primary prevention with a single zone at 200 bpm with a 2.5 second delay before the initiation of therapy was found to reduce inappropriate shock as well as mortality. This was also found with a three zone system with delayed therapy using a 60 second delay at 170 bpm, and a 12 second delay at 200 bpm and a 2.5 second delay at 250 bpm. A worse outcome was found for conventional programming using a 2 zone system with a 2.5 second delay at 170 bpm and a 1.0 second delay at 200 bpm. In general switching off ATP in VT zones as well as turning SVT discriminators are clearly not recommended. Which drugs have little to no effect on capture threshold? Beta blockers usually have little to no effect on capture threshold. Example: Metoprolol is clearly least likely to have elevated RV pacing thresholds in a patient. Name drugs that can increase pacing thresholds? Both class IC antiarrhythmics (propafenone, but flecainide in particular) as well as class III antiarrhythmics (amiodarone and sotalol) may lead to an increase in pacing thresholds. (Though sotalol can IMPROVE DFT). What factors increase risk for device infection? Immunosuppression (corticosteroid use) Renal dysfunction Oral anticoagulation (increase risk of hematoma and infection) Coexisting illnesses like diabetes Periprocedural issues (including the failure to administer properly timed pre op antimicrobial prophylaxis Device or lead revision (2-4x higher vs. initial implant) The amount of indwelling hardware (number of leads) and operator experience. Therapeutic dose low molecular weight heparin (LMWH) is associated with a substantial risk for perioperative bleeding and hematoma formation. In contrast, it has been shown to be much less in patients on Vitamin K antagonists such as warfarin even at therapeutic doses. Many operators now recommend uninterrupted warfarin therapy perioperatively especially for patients at high risk for thromboembolic events. Ibuprofen is associated with low risk, while aspirin and clopidogrel have an increased risk, but nowhere near as high as LMWH. How is energy consumption of the device calculated? What is Ohm's law? Energy = V x I x t (V = volts, I = current, t = time) V = IR E = V2 x t/R (R = resistance) Which bacteria is most likely to cause post op infection? Staphylococcus infection is responsible for 80% of all device infections. Infections months afterward is due to Staphylococcus epidermis. Acute, purulent device infections are usually caused by S. aureus. LV pacing is most often associated with what? LV pacing is most often associated with a RBBB pattern since the depolarization starts in the LV and arrives late in the RV. Stimulation of the RV apex and RV free wall will have what pattern? Stimulation of the RV apex and RV free wall will have a LBBB pattern. The RVOT has an inferior axis and LBBB pattern.