John Goldblatt

Epicardial wave mapping in human long-lasting persistent atrial fibrillation: transient rotational circuits, complex wavefronts, and disorganized activity

OBJECTIVES To characterize the nature of atrial fibrillation (AF) activation in human persistent AF (PerAF) using modern tools including activation, directionality analyses, complex-fractionated electrogram, and spectral information. BACKGROUND The mechanism of PerAF in humans is uncertain. METHODS AND RESULTS High-density epicardial mapping (128 electrodes/6.75 cm(2)) of the posterior LA wall (PLAW), LA and RA appendage (LAA, RAA), and RSPV-LA junction was performed in 18 patients with PerAF undergoing open heart surgery. Continuous 10 s recordings were analysed offline. Activation patterns were characterized into four subtypes (i) wavefronts (broad or multiple), (ii) rotational circuits (≥2 rotations of 360°), (iii) focal sources with centrifugal activation of the entire mapping area, or (iv) disorganized activity [isolated chaotic activation(s) that propagate ≤3 bipoles or activation(s) that occur as isolated beats dissociated from the activation of adjacent bipole sites]. Activation at a total of 36 regions were analysed (14 PLAW, 3 RSPV-LA, 12 LAA, and 7 RAA) creating a database of 2904 activation patterns. In the majority of maps, activation patterns were highly heterogeneous with multiple unstable activation patterns transitioning from one to another during each recording. A mean of 3.8 ± 1.6 activation subtypes was seen per map. The most common patterns seen were multiple wavefronts (56.2 ± 32%) and disorganized activity (24.2 ± 30.3%). Only 2 of 36 maps (5.5%) showed a single stable activation pattern throughout the 10-s period. These were stable planar wavefronts. Three transient rotational circuits were observed. Two of the transient circuits were located in the posterior left atrium, while the third was located on the anterior surface of the LAA. Focal activations accounted for 11.3 ± 14.2% of activations and were all short-lived (≤2 beats), with no site demonstrating sustained focal activity. CONCLUSION Human long-lasting PerAF is characterized by heterogeneous and unstable patterns of activation including wavefronts, transient rotational circuits, and disorganized activity.

Blunt traumatic aortic transection: the endovascular experience.

BACKGROUND Thoracic aortic transection resulting from blunt trauma is usually fatal. It is almost always associated with multiple, complex, nonaortic injuries that could be adversely affected by standard surgical repair of the aorta. Endovascular stenting techniques offer these patients a less physiologically disruptive treatment option. We studied the feasibility and safety of endovascular stent graft placement for treatment of acute traumatic aortic transection. METHODS Between 1994 and 2001, 9 patients were treated emergently for aortic transections with stent graft placement. The first patient had a custom-made prototype, and the other 8 patients had the Cook-Zenith thoracic stent graft implanted. All were polyester-covered Z-stent construction and deployed through a femoral 20- to 24-F delivery sheath. RESULTS Stent graft placement successfully sealed the aorta in all patients. One patient died as a result of a cerebrovascular accident. One patient required a brachial thrombectomy to relieve arm ischemia. The remaining eight patients were alive and without complications during the follow-up period (mean 21 months). CONCLUSIONS Endovascular repair for acute aortic transection is a safe, effective, and timely treatment option. It may be the treatment of choice in patients with extensive associated injuries.

The role of chronic atrial stretch and atrial fibrillation on posterior left atrial wall conduction.

BACKGROUND The posterior left atrium (LA) is involved in the initiation and maintenance of atrial fibrillation (AF). OBJECTIVE The purpose of this study was to compare conduction patterns on the posterior LA in patients with mitral regurgitation (MR), with and without AF. METHODS Epicardial mapping of the posterior LA was performed in 23 patients undergoing cardiac surgery. Patients were included in one of three groups: Group A-patients in sinus rhythm with normal left ventricular function undergoing coronary artery bypass grafting, Group B-patients in sinus rhythm with MR undergoing mitral valve surgery, or Group C-patients in persistent AF with MR undergoing mitral valve surgery. Conduction patterns, regional conduction velocity, conduction heterogeneity, conduction anisotropy, and complex fractionated atrial electrograms (CFAEs) were assessed. RESULTS LA diameter was greater in patients in Groups C (57 +/- 4mm) and B (54 +/- 6mm) than in Group A (39 +/- 7 mm, P <0.01). Patients in Group C had a greater number of lines of conduction delay than Groups A and B (2.0 +/- 0.8 vs 1 +/- 0 and 1 +/- 0, P <0.05). The extent of conduction delay and conduction heterogeneity was greater in Group C than in Group B, which was greater than in Group A (P <0.05). The percentage of CFAEs that remained stable during AF was 61% +/- 17%. There was a significant correlation between CFAEs during AF and regions of slow conduction during pacing (R = 0.36, P <0.001). CONCLUSION Patients with MR, LA enlargement, and AF have more extensive regions of conduction slowing in the posterior LA. Anatomically constant lines of conduction delay in this region lead to circuitous wavefront propagation. During persistent AF, fractionated electrograms in the posterior LA are distributed to regions demonstrating slow conduction, and the majority remain stable over time.

Anatomically Determined Functional Conduction Delay in the Posterior Left Atrium Relationship to Structural Heart Disease

OBJECTIVES This study sought to characterize the conduction properties of the posterior left atrium (PLA) in patients with different forms of structural heart disease undergoing cardiac surgery. BACKGROUND The PLA plays an important role in the initiation and maintenance of atrial fibrillation. METHODS This study included 34 patients having elective cardiac surgery. There were 4 groups of patients: normal left ventricular (LV) function (coronary artery bypass grafting [CABG]); severe LV dysfunction (LVF/CABG); severe mitral regurgitation (MR); severe aortic stenosis (AS). Epicardial mapping of the PLA was performed in sinus rhythm and during differential pacing. Activation patterns, regional conduction velocity (CV), conduction heterogeneity, anisotropy, and total plaque activation time (TAT) were assessed. RESULTS Left atrial size in patients with LVF/CABG (47 +/- 7 mm) and MR (54 +/- 6 mm) was larger than patients with CABG (39 +/- 7 mm) and AS (42 +/- 6 mm; p < 0.05). During pacing, all patients developed a vertical line of conduction delay running between the pulmonary veins. The extent of this conduction delay was greater in patients with LVF/CABG and MR than patients with AS and CABG (p < 0.05). Conduction heterogeneity, anisotropy, and TAT were greater in patients with LVF/CABG and MR than patients with CABG (p < 0.05). These changes resulted in circuitous wave front propagation. CONCLUSIONS There is a line of functional conduction delay in a consistent anatomical location in the PLA in patients with structural heart disease. This is most marked in conditions associated with significant chronic atrial enlargement and leads to circuitous wave front propagation, suggesting a potential role in arrhythmogenesis.

Acute atrial stretch results in conduction slowing and complex signals at the pulmonary vein to left atrial junction: insights into the mechanism of pulmonary vein arrhythmogenesis

Background—The pulmonary vein–left atrial (PV–LA) junction is key in pathogenesis of AF, and acute stretch is an important stimulus to AF. We aimed to characterize the response of the junction to acute stretch, hypothesizing that stretch would result in electrophysiological changes predisposing to re-entry. Methods and Results—Fifteen participants undergoing cardiac surgery underwent evaluation of the right superior PV–LA junction using an epicardial mapping plaque. In 10, this was performed before and after atrial stretch imposed by rapid volume expansion, and in 5, it was performed with an intervening observation period. Activation was characterized by conduction slowing and electrogram fractionation transversely across the PV–LA junction, with lines of block also demonstrated perpendicular to the junction. Conduction was decremental (plaque activation time 135.8±46.8 ms with programmed extra stimuli at 10 ms above effective refractory period versus 66.1±22.9 ms with pacing at 400 ms; P<0.001) and percentage fractionation was greater with programmed extra stimuli at 10 ms above (33.5%±15.3% versus 20.7%±14.0%, P=0.001). Right atrial pressure increased by 2.5±1.8 mm Hg (P=0.002) with volume expansion. Stretch resulted in conduction slowing across the PV–LA junction (increase in activation time 10.9±14.6 ms in acute stretch group versus −0.1±4.5 ms in control group; P=0.002). Conduction slowing was more marked with programmed extra stimuli at 10 ms above effective refractory period than with stable pacing (13.4±16.5 ms versus 1.7±5.4 ms; P=0.003). Stretch resulted in a significant increase in fractionated electrograms (7.9%±7.0% versus −0.4±3.3; P=0.004). Conclusions—Acute stretch results in conduction slowing across the PV–LA junction, with a greater degree of signal complexity. This substrate may be important in AF initiation and maintenance by promoting re-entry.

The effects of cardiopulmonary bypass on total and unbound plasma concentrations of propofol and midazolam.

OBJECTIVE To examine the effects of cardiopulmonary bypass (CPB) on total and unbound plasma concentrations of propofol and midazolam when administered by continuous infusion during cardiac surgery. DESIGN Prospective clinical study. SETTING University hospital. PARTICIPANTS Twenty-four adult patients undergoing cardiac surgery. INTERVENTIONS Patients received either propofol or midazolam to supplement fentanyl anesthesia. Twelve patients received a propofol bolus (1 mg/kg) followed by an infusion of 3 mg/kg/hr. A second group received midazolam, 0.2 mg/kg bolus, followed by an infusion of 0.07 mg/kg/hr. MEASUREMENTS AND MAIN RESULTS Blood sample were collected from the radial artery cannula at 0, 2, 4, 8, 8, 10, 15, 20 minutes and then every 10 minutes before CPB, at 1, 2, 3, 4, 6, 10, 15, 20 minutes and then each 10 minutes during CPB. On weaning from CPB samples were collected at 0, 5, 10 and 20 minutes. Plasma binding, total and unbound propofol and midazolam concentrations were determined by ultrafiltration and high-pressure liquid chromatography (HPLC). CPB resulted in a fall in total propofol and midazolam plasma concentrations, but the unbound concentrations remained stable. The propofol unbound fraction increased from 0.22 +/- 0.06% to 0.41 +/- 0.17%. The midazolam unbound fraction increased from 5.6 +/- 1.0% to 11.2 +/- 2.1%. CONCLUSIONS Unbound concentrations of propofol and midazolam are not affected by cardiopulmonary bypass. Total intravenous anesthesia algorithms do not need to be changed to achieve stable unbound plasma concentrations when initiating CPB.

High-density epicardial mapping of the pulmonary vein-left atrial junction in humans: Insights into mechanisms of pulmonary vein arrhythmogenesis

BACKGROUND The pulmonary veins (PVs) and the PV-LA (left atrium) junction are established sources of triggers initiating atrial fibrillation. In addition, they have been implicated in the maintenance of arrhythmia. OBJECTIVE To undertake high-density electrophysiological characterization of the right superior PV-LA junction in humans. METHODS Mapping was performed in 18 patients without a history of atrial fibrillation undergoing cardiac surgery. A high-density epicardial plaque was positioned at the anterior right superior pulmonary vein covering 3 regions: LA, PV-LA junction, and the PV. Isochronal maps were created during (1) sinus rhythm (SR); (2) LA pacing (LA-Pace); (3) PV pacing (PV-Pace); (4) LA programmed electrical stimulation (LA-PES); and (5) PV programmed electrical stimulation (PV-PES). Regional differences in conduction slowing/conduction block (CS/CB) and the prevalence of fractionated signals (FS) and double potentials (DPs) were assessed. RESULTS A region of isochronal crowding representing CS/CB developed at the PV-LA junction in 84% of the maps. Three distinct activation patterns were seen. Pattern 1: Uniform SR activation without CS/CB. LA-Pace and PES caused 1 to 2 lines of isochronal crowding (CS/CB) at the PV-LA junction. Pattern 2: CS/CB occurred at the PV-LA junction in SR. LA/PV-Pace and LA/PV-PES caused an increase in CS/CB at the PV-LA junction with widely split DPs and FS. Pattern 3: A single incomplete line of CS at the PV-LA junction in SR. With LA/PV pacing and LA/PV-PES, multiple lines (≥3) of CS/CB developed at the PV-LA junction with evidence of circuitous activation and a marked increase in DPs and FS. CONCLUSION High-density epicardial mapping of the right superior pulmonary vein demonstrates marked functional conduction delay and circuitous activation patterns at the PV-LA junction, creating the substrate for reentry.

The Ross procedure in adults presenting with bicuspid aortic valve and pure aortic regurgitation: 85% freedom from reoperation at 20 years

OBJECTIVES The Ross procedure has demonstrated excellent results when performed in patients with aortic stenosis or mixed aortic valve disease [aortic stenosis and aortic regurgitation (AR)]. However, due to its reported risk of late reoperation, it is not recommended under current guidelines for patients presenting with bicuspid aortic valve and pure AR. We have analysed our own results in light of this recommendation. METHODS Between 1993 and 2016, 129 consecutive patients with a mean age of 34.7 ± 10.6 years (range 16-64 years) presented with bicuspid aortic valve and pure AR and underwent the Ross procedure. Patients were reviewed annually and had 2nd yearly transthoracic echocardiograms during follow-up. The unit had a liberal reoperation policy where reoperation was performed if patients developed recurrent moderate or greater AR during follow-up. RESULTS There was 1 inpatient death, and 3 late deaths over a mean follow-up duration of 9.6 ± 6.8 years. Late survival at 10 and 20 years post-surgery were 99% [95% confidence interval (CI) 94-100] and 95% (95% CI 85-99), respectively. Eleven patients underwent redo aortic valve replacement (AVR) and 4 patients had redo pulmonary valve replacement. Freedom from reoperation for AVR and more-than-mild AR at 10 and 20 years post-surgery were 89% (95% CI 81-94) and 85% (95% CI 74-92), respectively. Having longer aortic cross-clamp (hazard ratio 1.03, 95% CI 1.00-1.06; P = 0.05) and cardiopulmonary bypass times (hazard ratio 1.02, 95% CI 1.00-1.05; P = 0.05), and having a larger preoperative sinotubular junction diameter (hazard ratio 1.15, 95% CI 1.03-1.30; P = 0.02) were significant predictors of having redo AVR or significant AR at follow-up. CONCLUSIONS With a 20-year freedom from redo AVR and greater-than-mild residual AR of 85%, the utilization of the Ross procedure in bicuspid aortic valve patients with pure AR should be considered.

Expanding cardiac pseudotumor.

FIGURE 1. Computed tomography scans. Long-axis images show dense calcification attached to the left ventricular endocardium and mitral annulus. LA, Left atrium; LV, left ventricle; A, Anterior; P, posterior; X, calcific mass. CLINICAL SUMMARY A 75-year-old woman presented with episodic presyncope associated with palpitations. She was diabetic and hypertensive with a history of rheumatic fever with associated valvular dysfunction. Physical examination revealed an irregular pulse rate of 82 beats/min and no signs of left heart failure. On auscultation, a soft diastolic murmur was heard. Biochemical investigation results were all within normal limits, including serum calcium, parathormone levels, and proteins C and S. Electrocardiography confirmed atrial fibrillation and showed periods of sinus rhythm and firstdegree heart block. In-hospital telemetry demonstrated episodes of complete heart block rate that required permanent pacemaker. Transthoracic and transesophageal echocardiography showed the presence of a large echogenic mass at the basal inferior wall and inferoposterior mitral annulus extending into both the interventricular and interatrial septae. The mass appeared encapsulated, intramyocardial, and extensive (5.4 3 4.2 cm). The posterior mitral valve leaflet was clearly compressed by the mass, causing mild mitral stenosis and mild mitral regurgitation. Left ventricular function was preserved. Transthoracic echocardiography, performed 3 years previously to investigate a diastolic murmur, revealed a 2.5 3 1.8-cm calcific mass behind the posterior mitral valve leaflet. The patient was lost to follow-up. Computed tomography (Figure 1) of the chest and cardiac magnetic resonance imaging confirmed the presence

Use of Transcatheter Valves for Open Surgical Mitral Valve Replacement. Australian Experience

BACKGROUND Mitral valve procedures remain a surgical challenge in the presence of extensive annular calcification, which presents a formidable technical challenge. Aggressive debridement is limited by risk of serious complications and the technical complexity of pericardial patch reconstruction of the debrided area. METHODS An open surgical approach with a transcatheter valve allows the valve to be placed under direct visualisation to facilitate positioning and to evaluate the likelihood of both perivalvular leakage and atrioventricular disruption. The open approach has the additional advantage of performing concomitant surgeries like other valve procedures, arrhythmias surgeries and coronary bypass. RESULTS We present our experience with open surgical mitral valve replacement (MVR) using transcatheter valve in different patients requiring varied procedures. These patients were not suitable for MVR using standard prosthetic valve and techniques. They were also not suitable for percutaneous MVR because of heavily calcified anterior mitral leaflet and the other concomitant procedures required. CONCLUSIONS Open MVR with a transcatheter balloon-expandable valve can avoid the need for technically challenging and high-risk decalcification of mitral annulus. These novel techniques using transcatheter valves can be successful in complex cases where standard prosthetic valves are impossible to implant in a heavily calcified mitral annulus.