Chest pain with ST segment elevation in a patient with prosthetic aortic valve infective endocarditis: a case report

<p>Abstract</p> <p>Introduction</p> <p>Acute ST-segment elevation myocardial infarction secondary to atherosclerotic plaque rupture is a common medical emergency. This condition is effectively managed with percutaneous coronary intervention or thrombolysis. We report a rare case of acute myocardial infarction secondary to coronary embolisation of valvular vegetation in a patient with infective endocarditis, and we highlight how the management of this phenomenon may not be the same.</p> <p>Case presentation</p> <p>A 73-year-old British Caucasian man with previous tissue aortic valve replacement was diagnosed with and treated for infective endocarditis of his native mitral valve. His condition deteriorated in hospital and repeat echocardiography revealed migration of vegetation to his aortic valve. Whilst waiting for surgery, our patient developed severe central crushing chest pain with associated anterior ST segment elevation on his electrocardiogram. Our patient had no history or risk factors for ischaemic heart disease. It was likely that coronary embolisation of part of the vegetation had occurred. Thrombolysis or percutaneous coronary intervention treatments were not performed in this setting and a plan was made for urgent surgical intervention. However, our patient deteriorated rapidly and unfortunately died.</p> <p>Conclusion</p> <p>Clinicians need to be aware that atherosclerotic plaque rupture is not the only cause of acute myocardial infarction. In the case of septic vegetation embolisation, case report evidence reveals that adopting the current strategies used in the treatment of myocardial infarction can be dangerous. Thrombolysis risks intra-cerebral hemorrhage from mycotic aneurysm rupture. Percutaneous coronary intervention risks coronary mycotic aneurysm formation, stent infections as well as distal septic embolisation. As yet, there remains no defined treatment modality and we feel all cases should be referred to specialist cardiac centers to consider how best to proceed.</p

Novel mapping and ablation approaches within myocardial scar

The arrhythmogenic substrate within myocardial scar contains regions of slow conduction that support reentry, characterized by low amplitude and fractionated electrograms (EGMs). Ablation therapy to prevent arrhythmias associated with such scar needs both accurate identification and interpretation of these EGMs and effective delivery of radiofrequency energy. This thesis explored new clinical approaches to the mapping and ablation of these EGMs within scar based arrhythmia. Previous studies from our institution have shown how robotically controlled catheters offer increased stability to achieve deeper lesions. At the start of this thesis, we demonstrated the feasibility of using the Hansen Robotic System within ventricular scar during post-infarct Ventricular Tachycardia (VT) ablation to reduce future implantable cardiac defibrillator (ICD) therapies. This included patients with advanced substrates having already incurred multiple previous ICD therapies. Having proven the possibility of robotic VT ablation, we investigated, as a randomised study, whether earlier substrate ablation after the first ICD therapy may improve outcomes. Earlier ablation delayed the time to VT recurrence compared to a non-ablative approach, though this did not reach statistical significance. In patients with LV ejection fraction >30%, ablation did significantly delay time to recurrence. In these studies, the substrate was broadly characterized by EGMs with bipolar voltage <1.5mV. Inaccurate delineation of the arrhythmogenic substrate may have been responsible for future VT recurrence. We analysed the effectiveness of increasing EGM resolution within scar using the ultra-high density Rhythmia system. This was preliminarily tested during post-AF ablation Atrial Tachycardia (AT) procedures, a more common and stable reentrant model than VT, but also involving complex circuits between scar and conductive tissue. Improving EGM/mapping resolution using the Rhythmia system was not entirely useful, as we were mis-lead by small rotational activations observed on most of the maps, the majority of which were pseudo-reentrant, often related to mis-annotation of EGM local activation time (LAT) and inaccurate interpolation of activation within regions of low voltage. An alternative means of displaying activation within scar without the need to reduce EGMs to a single LAT was required. Ripple Mapping (RM) was previously developed in our institution to provide this alternative means, and displays an EGM in its entirety as a moving bar on the map. We prospectively tested the feasibility of Ripple mapping within scar; we first developed a method of using RM to differentiate regions of ablation related scar from low voltage but functional tissue in iatrogenic ATs, and observed very high ablation success. This was reproducible during multi-centre studies. Within post-infarct ventricular scar, mapping in sinus rhythm/controlled pacing, RM helped us to differentiate local from far-field activation, especially with small tip and narrowly spaced electrodes, and visualise channels of delayed conduction through scar that collocated with the diastolic pathway mapped in VT, ablation of which reduced future VT recurrence. However, ablation within these ventricular channels did not eliminate future VT recurrence. We considered whether the lines of block bordering these channels may be functional by comparing the scar locations under different cycle lengths and activation directions. Remapping post ablation atrial scars under different cycle lengths and activation directions using RM demonstrated a generally fixed scar distribution. Within ventricular scars, where the diastolic pathway could be mapped in VT, in certain areas, it was formed of functional block during tachycardia with preserved EGMs in sinus rhythm; further studies within ventricular scar under different pacing rates and activation directions may better our understanding of the ventricular substrate. In conclusion, this thesis proposes that RM be considered the gold standard approach to mapping EGMs to determine the arrhythmogenic substrate in post ablation ATs. In post-infarct VT, undertaking ablation using robotic navigation after the first ICD therapy, specifically in patients with EF >30%, and using RM based approach to define this arrythmogenic substrate can help to improve outcomes.Open Acces

Controlled regional hypoperfusion in Langendorff heart preparations

We describe a new approach that combines several techniques to allow abnormal electrical and calcium activity to be visualized within hypoperfused myocardial tissue. A flexible microcannula was inserted into the left anterior descending artery of Langendorff perfused rat hearts, an air-tight seal between the coronary artery and the cannula was created, and an HPLC pump was used to deliver a specified flowrate through the microcannula. High resolution optical mapping of NADH/calcium, NADH/voltage or calcium/voltage was then conducted using a dual camera system. The ECG was acquired using surface electrodes. This perfusion technique is superior to occluding a vessel by either a tie or a clamp because it allows precise control of the composition and amount of flow to a defined ischemic bed. Another advantage is that flow can be stopped and resumed remotely, without touching the heart. This allows ectopic beats, or other arrhythmogenic activity, such as alternans, to be recorded immediately after changes in flow are imposed. Altogether, the described method provides a powerful new tool to assess how coronary flow rate affects the degree of local ischemia by the ability to record abnormal patterns of electrical activity and associated intracellular calcium transients with high spatiotemporal resolution from epicardial areas as small as 100 × 100 μm

Lesion metrics and 12-month outcomes of very-high power short duration radiofrequency ablation (90W/4 s) under mild conscious sedation.

Pulmonary vein isolation (PVI) is often performed under general anaesthesia (GA) or deep sedation. Anaesthetic availability is limited in many centers, and deep sedation is prohibited in some countries without anaesthetic support. Very high-power short duration (vHPSD-90W/4 s) PVI using the Q-Dot catheter is generally well tolerated under mild conscious sedation (MCS) though an understanding of catheter stability and long-term effectiveness is lacking. We analyzed lesion metrics and 12-month freedom from atrial arrythmia with this approach. Our approach to radiofrequency (RF) PVI under MCS is standardized and includes a single catheter approach with a steerable sheath. We identified patients undergoing Q-Dot RF PVI between March 2021 and December 2022 in our center, comparing those undergoing vHPSD ablation under MCS (90W/MCS) against those undergoing 50 W ablation under GA (50 W/GA) up to 12 months of follow-up. Data were extracted from clinical records and the CARTO system. Eighty-three patients met our inclusion criteria (51 90W/MCS; 32 50 W/GA). Despite shorter ablation times (353 vs. 886 s; p < .001), the 90 W/MCS group received more lesions (median 87 vs. 58, p < .001), resulting in similar procedure times (149.3 vs. 149.1 min; p = .981). PVI was achieved in all cases, and first pass isolation rates were similar (left wide antral circumferential ablation [WACA] 82.4% vs. 87.5%, p = .758; right WACA 74.5% vs. 78.1%, p = .796; 90 W/MCS vs. 50 W/GA respectively). Analysis of 6647 ablation lesions found similar mean impedance drops (10.0 ± 1.9 Ω vs. 10.0 ± 2.2 Ω; p = .989) and mean contact force (14.6 ± 2.0 g vs. 15.1 ± 1.6 g; p = .248). Only median 2.5% of lesions in the 90 W/MCS cohort failed to achieve ≥ 5 Ω drop. In the 90 W/MCS group, there were no procedural related complications, and 12-month freedom from atrial arrhythmia was observed in 78.4%. vHPSD PVI is feasible under MCS, with encouraging acute and long-term procedural outcomes. This provides a compelling option for centers with limited anaesthetic support

An approach to help differentiate postinfarct scar from borderzone tissue using Ripple Mapping during ventricular tachycardia ablation

BackgroundVentricular scar is traditionally highlighted on a bipolar voltage (BiVolt) map in areas of myocardium MethodsFifteen consecutive patients (left ventricular ejection fraction 30 ± 7%) underwent endocardial left ventricle pentaray mapping (median 5148 points) and ablation targeting areas of late Ripple activation. BiVolt maps were studied offline at initial voltage of 0.50-0.50 mV to binarize the color display (red and purple). RMs were superimposed, and the BiVolt limits were sequentially reduced until only areas devoid of Ripple bars appeared red, defined as RM-scar. The surrounding area supporting conducting Ripple wavefronts in tissue ResultsRM-scar was significantly smaller than the traditional 0.50 mV cutoff (median 4% vs. 12% shell area, p ConclusionPostinfarct scars appear significantly smaller than traditional 0.50 mV cut-offs suggest, with voltage thresholds unique to each patient