Peak Left Ventricular Outflow Tract Gradient Research Articles

Percutaneous alcohol septal ablation for hypertrophic obstructive cardiomyopathy: Technical review and long-term clinical and echocardiographic outcomes

BackgroundPercutaneous septal ablation by alcohol-induced septal branch occlusion was introduced as a new treatment option in symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM). Our aim was to evaluate procedural and long-term clinical and echocardiographic outcomes in patients with HOCM treated by alcohol septal ablation (ASA) at our center. MethodsThis single-center retrospective study included 14 consecutive HOCM patients undergoing percutaneous ASA (66.4±12.1 years, 71.4% female). At baseline all patients presented persistent symptoms despite optimized medical treatment, left ventricular outflow tract (LVOT) obstruction with a peak gradient >50mmHg, systolic anterior motion of the mitral valve, and ventricular septal thickness ≥15mm. ASA was considered successful when the LVOT pressure gradient fell to less than 50% of baseline value. All patients had echocardiographic evaluation at baseline, intraprocedure and at follow-up, and a long-term clinical follow-up (25±38 months) with evaluation of functional class and occurrence of symptoms or cardiovascular events. ResultsPercutaneous ASA achieved a 71.4% acute and 85.7% long-term success rate. Peak LVOT gradient decreased from 104±40mmHg at baseline to 58±30mmHg intraprocedure (p=0.03) and 35±26mmHg at follow-up (p=0.001); total gradient decrease was 75±43mmHg. Ventricular septal thickness and mitral regurgitation also presented significant decreases during follow-up (from 24±5mm to 18±4mm, p=0.02, and from grade 2.4±0.6 to 1.4±0.5, p<0.001, respectively). A tendency for long-term improvement in NYHA functional class (from 2.6±1.1 to 1.8±1.4, p=0.09) was observed. Procedural complications occurred in 6.7% of patients; two deaths and one transient ischemic attack occurred in-hospital, but no long-term clinical events were recorded. ConclusionsPercutaneous ASA is an effective treatment for symptomatic patients with HOCM, obtaining a marked decrease in LVOT pressure gradient and symptomatic improvement. Despite the occurrence of a significant number of procedural complications, the favorable long-term outcomes underline the potential of ASA as a percutaneous alternative to surgical myectomy.

Percutaneous alcohol septal ablation for hypertrophic obstructive cardiomyopathy: Technical review and long-term clinical and echocardiographic outcomes

BackgroundPercutaneous septal ablation by alcohol-induced septal branch occlusion was introduced as a new treatment option in symptomatic patients with hypertrophic obstructive cardiomyopathy (HOCM). Our aim was to evaluate procedural and long-term clinical and echocardiographic outcomes in patients with HOCM treated by alcohol septal ablation (ASA) at our center. MethodsThis single-center retrospective study included 14 consecutive HOCM patients undergoing percutaneous ASA (66.4±12.1 years, 71.4% female). At baseline all patients presented persistent symptoms despite optimized medical treatment, left ventricular outflow tract (LVOT) obstruction with a peak gradient >50mmHg, systolic anterior motion of the mitral valve, and ventricular septal thickness ≥15mm. ASA was considered successful when the LVOT pressure gradient fell to less than 50% of baseline value. All patients had echocardiographic evaluation at baseline, intraprocedure and at follow-up, and a long-term clinical follow-up (25±38 months) with evaluation of functional class and occurrence of symptoms or cardiovascular events. ResultsPercutaneous ASA achieved a 71.4% acute and 85.7% long-term success rate. Peak LVOT gradient decreased from 104±40mmHg at baseline to 58±30mmHg intraprocedure (p=0.03) and 35±26mmHg at follow-up (p=0.001); total gradient decrease was 75±43mmHg. Ventricular septal thickness and mitral regurgitation also presented significant decreases during follow-up (from 24±5mm to 18±4mm, p=0.02, and from grade 2.4±0.6 to 1.4±0.5, p<0.001, respectively). A tendency for long-term improvement in NYHA functional class (from 2.6±1.1 to 1.8±1.4, p=0.09) was observed. Procedural complications occurred in 6.7% of patients; two deaths and one transient ischemic attack occurred in-hospital, but no long-term clinical events were recorded. ConclusionsPercutaneous ASA is an effective treatment for symptomatic patients with HOCM, obtaining a marked decrease in LVOT pressure gradient and symptomatic improvement. Despite the occurrence of a significant number of procedural complications, the favorable long-term outcomes underline the potential of ASA as a percutaneous alternative to surgical myectomy.

094 Long-term follow-up after alcohol septal ablation for hypertrophic obstructive cardiomyopathy in young adults

Results: During the study period, 21 patients (15 males) aged between 18 and 40 years old (mean age 33.1±5.6, range 18-39 years) underwent ASA. Among them, 76% were treated with beta-blockers, 33% calcium-channel antagonists and 5% disopyramide. There were 6 patients (29%) with prior pacemaker, 1 patient (5%) with history of sudden death and prior implantable cardioverter-defibrillator (ICD) and 1 patient (5%) with prior myectomy. At baseline, mean New York Heart Association (NYHA) functional class was 2.4±0.5. Mean left ventricular outflow tract (LVOT) peak gradient and septal thickness were 89±37 mmHg and 24.9±5.1 mm, respectively. All procedures were performed with myocardial contrast echocardiography guidance. During ASA, 2.2±0.7 ml of absolute alcohol was injected in 1.4±0.5 septal perforators. Final procedural LVOT peak gradient was 20±16mmHg. Procedural success (defined as immediate LVOT peak gradient reduction >50%) was achieved in 20 patients (95%). There were no major complications. One patient (5%) required a temporary pacemaker for second-degree atrioventricular block. Mean peak CK was 934±468 IU/L. At a mean follow-up of 3.0±2.0 years after the procedure (range 0.3-8.4), repeat ASA was performed in two patients (10%) and a new ICD was needed in 1 patient (5%), while there were no fatalities reported. Mean NYHA class was improved to 1.6±0.7.

Negative Ionotropic Agents for the Treatment of Left Ventricular Outflow Tract Obstruction Due to Sigmoid Septum and Concentric Left Ventricular Hypertrophy

Negative ionotropic agents are established treatments for left ventricular outflow tract obstruction (LVOTO) in hypertrophic cardiomyopathy (HCM). However, their benefit in those with LVOTO without typical HCM is unclear. We evaluated if negative ionotropic agents are beneficial in treatment of LVOTO in patients without typical HCM. In this retrospective cohort study, we evaluated echocardiograms and reviewed records of 15 patients with resting LVOT obstruction due to sigmoid septum (SS, n=9) and mild concentric left ventricular hypertrophy (LVH, n=6). Patients received treatment with sequential negative ionotropic agents (β-blockers and disopyramide). Initial symptoms, presentation characteristics and echocardiographic characteristics pre and post treatment were evaluated. Fifteen patients (mean age 66.2 years, 46.7% male) were included. Dyspnoea (NYHA Class II/III) was reported as the initial symptom in all patients with four patients reporting chest pain. All patients had hypercontractile LV function at baseline (fractional shortening 46.29±8.77%) but had normal LVS/PW ratio (1.03±0.10). The mean resting LVOT gradient was 74.4±55.2 mmHg. Fourteen patients received initial β-blocker therapy with a mean reduction in peak LVOT gradient of 40.9 mmHg seen in 11 patients that responded to therapy (p=0.02). Nine patients received disopyramide with a further 24.2±25.8 mmHg reduction in peak LVOT gradient observed in eight patients who tolerated treatment (p=0.04). Symptomatic improvement occurred in 80% of treated patients. In patients with LVOTO without typical HCM, sequential treatment with negative ionotropes is associated with a significant reduction in the degree of LVOTO and leads to symptomatic improvement.

Effects of alcohol septal ablation on coronary microvascular function and myocardial energetics in hypertrophic obstructive cardiomyopathy

This study investigated the effects of alcohol septal ablation (ASA) on microcirculatory function and myocardial energetics in patients with hypertrophic cardiomyopathy (HCM) and left ventricular outflow tract (LVOT) obstruction. In 15 HCM patients who underwent ASA, echocardiography was performed before and 6 mo after the procedure to assess the LVOT gradient (LVOTG). Additionally, [(15)O]water PET was performed to obtain resting myocardial blood flow (MBF) and coronary vasodilator reserve (CVR). Changes in LV mass (LVM) and volumes were assessed by cardiovascular magnetic resonance imaging. Myocardial oxygen consumption (MVo(2)) was evaluated by [(11)C]acetate PET in a subset of seven patients to calculate myocardial external efficiency (MEE). After ASA, peak LVOTG decreased from 41 ± 32 to 23 ± 19 mmHg (P = 0.04), as well as LVM (215 ± 74 to 169 ± 63 g; P < 0.001). MBF remained unchanged (0.94 ± 0.23 to 0.98 ± 0.15 ml·min(-1)·g(-1); P = 0.45), whereas CVR increased (2.55 ± 1.23 to 3.05 ± 1.24; P = 0.05). Preoperatively, the endo-to-epicardial MBF ratio was lower during hyperemia compared with rest (0.80 ± 0.18 vs. 1.18 ± 0.15; P < 0.001). After ASA, the endo-to-epicardial hyperemic (h)MBF ratio increased to 1.03 ± 0.26 (P = 0.02). ΔCVR was correlated to ΔLVOTG (r = -0.82; P < 0.001) and ΔLVM (r = -0.54; P = 0.04). MEE increased from 15 ± 6 to 20 ± 9% (P = 0.04). Coronary microvascular dysfunction in obstructive HCM is at least in part reversible by relief of LVOT obstruction. After ASA, hMBF and CVR increased predominantly in the subendocardium. The improvement in CVR was closely correlated to the absolute reduction in peak LVOTG, suggesting a pronounced effect of LV loading conditions on microvascular function of the subendocardium. Furthermore, ASA has favorable effects on myocardial energetics.

Midterm follow-up of arterial switch operation for transposition of the great arteries with intact ventricular septum and left-ventricular outflow tract obstruction☆

We report the mid-term follow-up of patients, who underwent arterial switch operation (ASO) for transposition of the great arteries (TGA) with intact ventricular septum and left-ventricular outflow tract obstruction (LVOTO) over a 10-year period from 2000 to 2009. Thirteen TGA patients (3.9% of our ASO cohort) with intact ventricular septum and LVOTO underwent ASO. LVOTO was defined as pulmonary valve z-score ≤ -2.0 (n=3) or peak LVOT gradient ≥40 mmHg with (n=7) or without (n=3) anatomic subvalvar stenosis on echocardiography. Median age and weight were 14 days (range, 7-130 days) and 3.2 kg (range, 2.1-4.6 kg). The LVOT abnormalities included fibromuscular narrowing (n=5) and atrioventricular valve-related findings (n=5). LVOT clearance was achieved by resection of accessory mitral tissue (n=2) only. Follow-up was 100% complete. There were no early or late deaths. Freedom from re-operation for neo-aortic valve regurgitation and/or LVOTO was 100% at a median follow-up of 38 months (range, 6-115 months). All patients had functional status appropriate for their age. Three patients had mild aortic regurgitation. The median Doppler estimated LVOT systolic gradient was 12 mmHg (range, 0-18 mmHg) for the entire cohort at the latest follow-up. Mid-term outcomes of ASO for a highly selected group of patients with pulmonary valve annulus z-score ≤ -2.0 ≥ -0.4, resectable organic LVOTO, and dynamic peak LVOT gradient ≥40 mmHg remain satisfactory, with a need for long-term follow-up.

Myocardial Fibrosis Assessed by Cardiac Magnetic Resonance Predicts Future Ventricular Arrhythmia in Subjects with Cardiomyopathy

We sought to determine whether LA dilatation in hypertrophic obstructive cardiomyopathy (HOCM) resolves following successful percutaneous transluminal septal myocardial ablation (PTSMA). Methods: Twenty-four patients (15 male, 59± 15 years) with severe HOCM underwent successful PTSMA. Echocardiography at baseline and 1-year post-procedure includedassessment of left ventricular (LV)wall thickness, LV gradients, mitral annular tissue Doppler velocities and mitral regurgitation. LA volume was measured using the single-plane area–length method in the apical fourchamber view and indexed to body surface area. A subgroup of 14 patients had repeat studies at 2 years. Results: In comparison with baseline, at 1 year following PTSMA there was a significant reduction in LV outflow tract peak gradient at rest (95± 45 vs. 23± 27mmHg, p< 0.001) and during Valsalva provocation (102± 43 vs. 35± 41mmHg, p= 0.002). Septal thickness (2.1± 0.4 vs. 1.7± 0.6 cm, p= 0.002), peak systolic velocity at the septal annulus (6.01± 1.23 vs. 5.38± 1.21 cm/s, p< 0.001) and grade ofmitral regurgitation (3± 1 vs. 2± 1, p< 0.001)were also reduced at 1 year. There was a significant 18% reduction in indexed LA volume from 60± 23ml/m2 at baseline to 49± 17ml/m2 at 1 year (p= 0.007). There was no further decrease in LA volume at 2 years (48± 19ml/m2, p=NS). Conclusions: Successful PTSMA in patients with severe HOCM is accompanied by a significant reduction in LA Results: Mean patient age was 60.4± 11.96 years with meanLVejection fraction of 23± 7.7%.RadialVVI-derived measurement of LV dyssynchrony correlated best with CMR-derived values (r= 0.84, p< 0.0001). Longitudinal VVI-derived measurement of dyssynchrony had a lower but still significant correlation with CMR-derived values (r= 0.67, p< 0.0001). Similarly, the VVI-derived longitudinal maximal delay correlated with the radial delayed (r= 0.69, p< 0.001). More patients were categorised as having dyssynchrony using the VVI radial delay (n= 21) compared to the CMR radial delay (n= 19). Conclusion: VVI-derived radial delay has significant correlation with CMR-derived measures and can be used for assessment and follow up assessment for dyssynchrony. Both radial and longitudinal delays in contraction complement each other and should both be used in the assessment of LV dyssynchrony. doi:10.1016/j.hlc.2008.05.142

Echocardiographic Evidence of the Brockenbrough???Braunwald???Morrow Sign After Mitral Valve Repair

The Brockenbrough–Braunwald–Morrow sign was first described in 1961 (1) in individuals with hypertrophic cardiomyopathy and dynamic left ventricular (LV) outflow tract (LVOT) obstruction worsened by conditions associated with increased myocardial contractility. The sign was characterized by an increase in peak-systolic gradient combined with a decrease in pulse pressure after an extrasystolic beat (2). The increased contractile performance in the postextrasystolic beat was explained by postextrasystolic potentiation from 1) persistence of the positive inotropic effect and 2) rest potentiation from an increased strength of contractility immediately after a period of rest (3). The pathophysiology underscoring the Brockenbrough– Braunwald–Morrow sign was demonstrated echocardiographically after repair of the mitral valve. A 58-yr-old female patient with severe mitral regurgitation from myxomatous degeneration underwent mitral valve repair that included a sliding quadrangular resection of the P2 (middle) segment of the posterior mitral valve leaflet and a 34-mm mitral ring annuloplasty (Model 4450, Edwards Life Sciences). Preprocedural transesophageal echocardiography (TEE) revealed a mitral valve with advanced myxomatous degeneration, redundant tissue of both leaflets and severe, central mitral regurgitation. After repair, color flow Doppler in the TEE midesophageal-aortic valvelong axis view demonstrated turbulent flow in the LVOT and mild mitral regurgitation consistent with systolic anterior motion (SAM) of the mitral valve (Fig. 1; also please see video loop available at www.anesthesiaanalgesia.org). Continuous-wave Doppler examination in the TEE transgastric mid-LV-long axis view measured a LVOT peak gradient of 60 mm Hg in the absence of aortic stenosis or septal hypertrophy. The presence of SAM ultimately led to a return to cardiopulmonary bypass and revision of the mitral valve repair (please see video loop available at www.anesthesiaanalgesia.org). In addition to SAM, further evidence for dynamic LVOT obstruction was captured on continuous-wave Doppler examination (Fig. 2). In this image, a premature complex led to a poor ejection and a reduced gradient. However, the postextrasystolic beat led to an increased LVOT gradient (VMAX 4.2 m/s; peak gradient 67.2 mm Hg; mean gradient 33.2 mm Hg). Continuouswave Doppler-derived measurements, taken immediately before the premature complex, demonstrated a consistent This article has supplementary material on the Web site: www.anesthesia-analgesia.org.

Relationship Between Outflow Obstruction and Left Ventricular Functional Impairment in Hypertrophic Cardiomyopathy: A Doppler Echocardiographic Study

Left ventricular outflow tract (LVOT) obstruction is predictive of a worse outcome in hypertrophic cardiomyopathy (HCM). In a detailed Doppler echocardiographic study of 178 selected HCM patients, the group of patients (n = 73) with the obstructive form (resting peak gradient > or = 30 mmHg) presented more hypertrophy and poorer systolic and diastolic left ventricular (LV) functions than the HCM group (n = 105) without obstruction. LVOT peak gradient was positively correlated with hypertrophy (P < 0.0001) and negatively to tissue Doppler mitral annulus systolic (P = 0.0001) and early diastolic (P < 0.0001) velocities. The gradient significantly correlated with E/Ea ratio (r = 0.67; P < 0.0001). By multiple regression, LVOT gradient was related to E/Ea, LV maximal thickness and left atrial size. In comparison with patients without obstruction, patients with obstruction presented greater hypertrophy (P < 0.0001), lower systolic and early diastolic mitral annulus velocities (both P < 0.0001), higher E/Ea ratio (P < 0.0001) and higher global function index (P < 0.0001). In HCM, beyond the effects on hypertrophy, LVOT obstruction is an independent determinant of LV functional abnormalities.

Long-Term Effects of Dual-Chamber Pacing With Periodic Echocardiographic Evaluation of Optimal Atrioventricular Delay in Patients With Hypertrophic Cardiomyopathy >50 Years of Age

Various treatment modalities have been introduced to reduce the subaortic pressure gradient in patients with obstructive hypertrophic cardiomyopathy, including pacemaker insertion. Complete ventricular capture during pacing is essential and requires optimization of the atrioventricular interval (AVI). In this study, a protocol using echocardiographic examination assessing the changes in the left ventricular outflow tract (LVOT) gradient in different AVIs, pacing rates, and pacing modes was used for optimal pacemaker programming. Twenty-five patients with obstructive hypertrophic cardiomyopathy were implanted with DDD pacemakers and evaluated prospectively. The LVOT gradient was measured during periodic evaluations every 3 to 6 months. Gradient measurements were done with 5 different AVIs and 3 different rate combinations. After each evaluation, the optimal AVI, pacing rate, and mode were set on the basis of the minimal LVOT gradient not associated with systolic arterial cuff pressure reduction. Follow-up ranged from 18 to 126 months. Peak LVOT gradient immediately decreased in 92% of patients. During follow-up, the optimal AVI was prolonged in most patients. Sixty-four percent of patients showed a clear relation between pacemaker modifications and gradient reduction. In 75% of these patients, optimal gradient reduction required repeated AVI and pacing rate programming on the basis of echocardiographic evaluation. Symptoms decreased in 92% of patients, and New York Heart Association class improved significantly (3.1+/-0.7 vs 1.3+/-0.4, p<0.001) during follow-up. The symptomatic reduction was positively correlated with the LVOT gradient reduction. In conclusion, DDD pacing is effective in reducing the LVOT gradient and improving functional capacity in adult patients with hypertrophic cardiomyopathy. Pacemaker programming with the periodic echocardiographic evaluation of the optimal AVI, pacing rate, and mode is imperative for optimal results.

Mitral regurgitation in hypertrophic obstructive cardiomyopathy: relationship to obstruction and relief with myectomy

OBJECTIVESThis study examined: 1) the impact of myectomy on postoperative mitral regurgitation (MR) and 2) the association between the severity of MR and the left ventricular outflow tract (LVOT) gradient.BACKGROUNDFor patients with hypertrophic obstructive cardiomyopathy (HOCM) and MR, controversy exists as to whether myectomy alone is sufficient in eliminating MR. Furthermore, the relationship between the degree of MR and the LVOT peak gradient has not been well defined.METHODSWe performed pre- and postoperative transthoracic as well as intraoperative transesophageal studies in 104 consecutive patients with HOCM undergoing septal myectomy. Left ventricular outflow tract gradient and the nature of MR were assessed.RESULTSIn the 93 patients without independent mitral valve disease, a relationship was observed between MR severity and the LVOT gradient. Left ventricular outflow tract gradient (mean ± standard deviation) for trivial, mild, moderate and severe MR were: 23.2 ± 19.1, 43.8 ± 25.4, 70.1 ± 21.0 and 104 ± 21.0 mm Hg (p < 0.001). Early postoperative, MR was absent or trivial in 80%, mild in 19% and moderate in 1%. None of these patients required additional mitral valve surgery. For patients with independent mitral valve disease (n = 11), five required mitral valve surgery as well as myectomy. The remainder had significant reductions in the degree of MR with myectomy alone.CONCLUSIONSFor patients with HOCM and MR not due to independent mitral valve disease, myectomy significantly reduced the degree of MR, without requirement for additional mitral valve surgery. In these patients the severity of MR was directly related to the magnitude of the LVOT gradient.

Mitral Valve Repair and Septal Myectomy for Hypertrophic Obstructive Cardiomyopathy

Combined mitral valve repair using the sliding leaflet technique and septal myectomy were employed to successfully treat left ventricular outflow tract (LVOT) obstruction and mitral regurgitation due to hypertrophic obstructive cardiomyopathy (HOCM). A 46-year-old man was diagnosed with HOCM along with congestive heart failure and was treated medically. These symptoms, however, were resistant to medical treatments with a beta-blocker, a Ca-antagonist, and disopyramide, and he was referred to our hospital for surgery. Doppler echocardiography demonstrated an LVOT obstruction at rest with a peak pressure gradient of 138 mmHg. The interventricular septum thickness was 14 mm. Mitral regurgitation of 3+ with severe SAM was also observed. Temporary dual chamber pacing was tried without significant improvement. Following these examinations, the patient underwent surgery. A transaortic septal myotomy-myectomy was performed first, and the mitral valve was then approached through the left atrium. Mitral valve repair was performed with the sliding leaflet technique to reduce the height of the posterior leaflet from 2 cm to 1 cm. Postpump transesophageal echocardiography revealed no MR and a peak LVOT gradient of 15 mmHg. The patient recovered well except for a residual mild SAM, and MR2+. We therefore concluded that this surgical approach might provide results which are superior to those of myectomy alone.

Benefits of Early Surgical Repair in Fixed Subaortic Stenosis

Objectives. We sought to determine whether early resection can improve outcome in fixed subaortic stenosis.Background. The diagnosis of subaortic stenosis (SAS) is often made before significant gradients occur. Whereas resection is the accepted treatment, it remains uncertain whether surgical intervention at this early stage can reduce the incidence of recurrence or influence the progression of aortic valve damage.Methods. Follow-up was available for 75 of 83 consecutive patients operated on for fixed SAS; the average duration of follow-up was 6.7 years. The lesion was discrete in 68 patients (91%) and of a tunnel type in 7, with associated ventricular septal defect in 28 (37%). All underwent transaortic resection.Results. There were no deaths. There were 18 recurrences of SAS in 15 patients (20%). Thirteen patients (17%) underwent 17 reoperations for recurrence or aortic valve disease. The cumulative hazard of recurrence was 8.9%, 16.1% and 29.4% ± 2.3% (mean ± SEM), and the hazard of events, including recurrence and reoperation, was 9.2%, 18.4% and 35.1% ± 3.5% at 2, 5 and 10 years, respectively. Residual end-operative left ventricular outflow tract (LVOT) gradients (>10 mm Hg, n = 8) and tunnel lesions were univariate predictors of recurrence (p = 0.0006 and p = 0.003, respectively). Multivariate predictors included higher preoperative LVOT gradient (p < 10−4) and younger patient age (p = 0.002). Only two recurrences (0.87 per 100 patient-years of follow-up) were noted in patients with a preoperative peak LVOT gradient ≤40 mm Hg (n = 40), whereas higher gradients (n = 35) were associated with a greater than sevenfold recurrence rate (6.45 events per 100 patient-years, p = 0.002). The aortic valve required concomitant repair in 17 cases in the high gradient group (48.6%) but in only 8 in the low gradient group (20%, p = 0.018). Despite relief of the obstruction, progressive aortic regurgitation was noted at follow-up after 14 procedures in the high gradient group (40%) but after only 5 procedures in the low gradient group (12.5%, p = 0.014).Conclusions. The data suggest that surgical resection of fixed subaortic stenosis before the development of a significant (>40 mm Hg) outflow tract gradient may prevent recurrence, reoperation and secondary progressive aortic valve disease.

Aortic root replacement with the pulmonary autograft in children with complex left heart obstruction

The optimal surgical treatment of complex (multiple level or recurrent) left ventricular outflow tract obstruction (LVOTO) in infancy is controversial. Staged procedures expose the children to the need for reoperation, and currently available techniques of aortoventriculoplasty are associated with the morbidities of biological and mechanical prostheses. Between July 1992 and January 1996, we have performed 24 aortic root replacements with the pulmonary autograft in pediatric patients (< 18 years). Of this group, 8 were infants and children with complex LVOTO aged 9 days to 22 months (mean, 8.6 +/- 8 months) and weighing 3.3 to 10.2 kg (mean, 6.3 +/- 2.6 kg). The diagnoses were interrupted aortic arch/ventricular septal defect/subaortic stenosis in 3, recurrent aortic stenosis in 2, aortic stenosis and subaortic stenosis in 1, and aortic stenosis/subaortic stenosis/mitral stenosis/regurgitation in 2. All patients had undergone one to three previous operative procedures (mean, 1.5 +/- 0.8 procedures/patient). Preoperative echocardiographic peak LVOT gradient was 71.7 +/- 25 mm Hg (range, 40 to 110 mm Hg) and aortic annulus size was 7.2 +/- 2.3 mm (range, 4 to 10.6 mm). The surgical technique included replacement of the aortic root with the pulmonary autograft combined with incision of the conal septum to relieve subaortic stenosis or accommodate for size discrepancy between the aortic and pulmonary autograft root and a pulmonary homograft placed in the right ventricular outflow tract. There were no perioperative or late deaths at follow-up (range, 2 to 25 months; mean, 13.5 +/- 8 months). Mean hospital stay was 15 +/- 17 days (range, 4 to 53 days). Three children had the following complications: diaphragmatic paresis (1), delayed pericardial effusion (1), and atrioventricular block requiring a pacemaker (1). In follow-up, echocardiographic findings showed absent aortic regurgitation in 3 and trivial aortic regurgitation in 5, and no significant LVOTO (mean peak gradient, 6.2 +/- 7.6 mm Hg; range, 0 to 16 mm Hg). Pulmonary homograft regurgitation was absent in 5, trivial in 2, and moderate in 1. Peak right ventricular outflow tract gradient by echocardiogram was trivial in 7, and a significant gradient of 55 mm Hg has developed in 1 infant. There were no infective or embolic complications during follow-up. Our experience shows that aortic root replacement with the pulmonary autograft can be performed in children with excellent clinical results. The technique of root replacement combined with ventriculoplasty allows definitive and simultaneous relief of complex and multiple-level obstructive lesions. Considering the growth potential of the pulmonary autograft, this should be regarded as the optimal treatment modality in infants with complex LVOTO:

901-23 Atrial Synchronous Versus AV Sequential Pacing for Hypertrophic Cardiomyopathy (HOCM)

Dual chamber (DC) pacing has proven effective in reducing the left ventricular outflow tract gradient (LVOTG) in most patients (pts) with HOCM refractory to drug therapy. However, optimal pacemaker (PM) programming including pacing mode and atrioventricular delay (AVD) has not been established. Accordingly, we performed continuous-wave transthoracic Doppler echocardiography on 7 pts with DC PMs (5 male, 2 female, mean age 64.7 ± 12.7 yearsl with HOCM and a resting peak LVOTG exceeding 25 mmHg to evaluate the effects on peak LVOTG of atrial synchronous pacing (VDD) and AV sequential pacing (DDD) at 10 bpm above sinus rhythm while varying the AVD in steps of 20 msec to a minimum of 40 msec 1) At AVD of 100 to 140 msec, DDD pacing significantly reduced the peak LVOTG while VDD pacing did not. 2) At AVD less than 100 msec, VDD pacing significantly reduced peak LVOTG only at AVD of 40 msec, while DDD pacing at 10 bpm above sinus rhythm reduced peak LVOTG at all AVD used. Therefore PMs which have the capabilityto program different AVD for VDD and DDD modes and that provide programmable AVDs less than 60 msec are optimal for HOCM pts.