Amyl Nitrite Inhalation Research Articles

Repetitive Squat-to-Stand Provocation of Dynamic Left Ventricular Outflow Tract Obstruction in Hypertrophic Cardiomyopathy

Left ventricular outflow tract (LVOT) obstruction is a determinant in the management of patients with hypertrophic cardiomyopathy, including candidacy for septal reduction therapy and risk stratification for sudden cardiac death. 1 Elliott P.M. Gimeno J.R. Tomé M.T. Shah J. Ward D. Thaman R. et al. Left ventricular outflow tract obstruction and sudden death risk in patients with hypertrophic cardiomyopathy. Eur Heart J. 2006; 27: 1933-1941 Crossref PubMed Scopus (262) Google Scholar ,2 Ommen S.R. Mital S. Burke M.A. Day S.M. Deswal A. Elliott P. et al. 2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy. J Am Coll Cardiol. 2020; 76: e159-e240 Crossref PubMed Scopus (136) Google Scholar Obstruction is defined as a maximal instantaneous gradient ≥ 30 mm Hg, and severe obstruction is defined as a maximal instantaneous gradient ≥ 50 mm Hg. 2 Ommen S.R. Mital S. Burke M.A. Day S.M. Deswal A. Elliott P. et al. 2020 AHA/ACC guideline for the diagnosis and treatment of patients with hypertrophic cardiomyopathy. J Am Coll Cardiol. 2020; 76: e159-e240 Crossref PubMed Scopus (136) Google Scholar Several provocative maneuvers have been used to elicit latent obstruction, including the Valsalva maneuver, amyl nitrite inhalation, and exercise on a treadmill or bike. 3 Marwick T.H. Nakatani S. Haluska B. Thomas J.D. Lever H.M. Provocation of latent left ventricular outflow tract gradients with amyl nitrite and exercise in hypertrophic cardiomyopathy. Am J Cardiol. 1995; 75: 805-809 Abstract Full Text PDF PubMed Scopus (74) Google Scholar , 4 Jensen M.K. Havndrup O. Pecini R. Dalsgaard M. Hassager C. Helqvist S. et al. Comparison of Valsalva manoeuvre and exercise in echocardiographic evaluation of left ventricular outflow tract obstruction in hypertrophic cardiomyopathy. Eur J Echocardiogr. 2010; 11: 763-769 Crossref PubMed Scopus (24) Google Scholar , 5 Shah J.S. Esteban M.T.T. Thaman R. Sharma R. Mist B. Pantazis A. et al. Prevalence of exercise-induced left ventricular outflow tract obstruction in symptomatic patients with non-obstructive hypertrophic cardiomyopathy. Heart. 2008; 94: 1288-1294 Crossref PubMed Scopus (165) Google Scholar During a recent shortage of amyl nitrite, our practice implemented a repetitive squat-to-stand maneuver as an adjunct to the Valsalva maneuver when assessing for LVOT obstruction. We sought to evaluate the efficacy of this repetitive squat-to-stand maneuver in eliciting LVOT obstruction compared with the Valsalva maneuver in a retrospective study.

Amyl nitrite inhalation, a “volatile” anemia

Amyl nitrite inhalation, a “volatile” anemia

Silas Weir Mitchell on epilepsy therapy in the late 19th to early 20th centuries.

Silas Weir Mitchell (1829-1914), one of the fathers of American neurology, is well known for many contributions to neurology. However, his efforts in epilepsy are overshadowed by his other accomplishments. Mitchell introduced a new bromide preparation, lithium bromide, as a viable therapy. His most widely accepted contribution to the field was the introduction of inhaled amyl nitrite for early termination of seizures accompanied by an appropriate aura. Despite the prevalent views on lifestyle modification as a treatment for epilepsy during this time period, as well as Mitchell's own development of the "rest cure" for certain disease states, he was not a proponent of these types of interventions for epilepsy, nor did he support interventions focused on other organ systems, such as abdominal or gynecologic surgery. Mitchell had distinct opinions on the treatment of epilepsy, and helped to advance its therapeutics during his career.

Contribution of "en face" SD‐OCT in retinal toxicity

AbstractPURPOSE: To assess retinal and choroidal changes in drug‐induced retinal toxicity using "en‐face" and BScan OCT images. METHODS: All patients underwent complete ophthalmologic examination, including fundus examination and autofluorescence, color photography, fluorescein and indocyanin green angiography. Type, amount and time of drug intake was precisely assessed. RESULTS: 8 patients were analysed and included retrospectively. Retinal toxicity was induced by tamoxifen in 2 cases, by synthetic antimalarial (SAM) drug in 3 cases and by inhaled amyl nitrite ("poppers") in 3 cases. The angiographic features, B‐Scan and "en‐face" OCT scans findings were correlated. In all cases, "en‐face" OCT provided precise anatomic location of the retinal layers involved, the extend of retinal damage, as well as follow‐up of these changes. CONCLUSION: "En‐face" OCT allows full imaging and better understanding of retinal toxicity induced by tamoxifen, SAM drugs and amyl nitrite.

Expanding the indications for septal myectomy in patients with hypertrophic cardiomyopathy: Results of operation in patients with latent obstruction

Many patients with symptomatic hypertrophic cardiomyopathy have minimal left ventricular outflow tract gradients, and there is uncertainty whether their limitation is due to diastolic dysfunction or labile outflow tract obstruction. The purpose of this study was to characterize the clinical presentation and outcome of septal myectomy in patients with hypertrophic cardiomyopathy and latent obstruction. Among 749 patients who underwent septal myectomy, 249 had latent obstruction with minimal (0-30 mm Hg) resting gradients preoperatively. All were symptomatic and had more severe left ventricular outflow tract obstruction provoked by Valsalva maneuver or amyl nitrite inhalation during Doppler echocardiography or by stimulation with isoproterenol during catheterization. Clinical characteristics, survival, and functional outcome of these patients were compared with those of 500 patients with more severe resting left ventricular outflow tract obstruction who underwent myectomy during the same period. Compared with those with severe obstruction, more patients with latent obstruction were male (63% vs 52%, P < .003), but ages were similar (53 ± 14 years vs 52 ± 15 years). Preoperative symptoms and functional limitation were similar in the 2 groups with 86% and 85%, respectively, having New York Heart Association class III or IV disability. Among patients with latent obstruction, mixed venous oxygen saturation was 61.6% ± 19.0% of predicted compared with 56.8% ± 17.3% for those with severe resting obstruction (P < .008). Septal thickness was less in patients with latent obstruction (20 ± 9 mm vs 22 ± 15 mm, P < .001). Early mortality was 1% in each group, and survival at 5 and 10 years was 93% and 87%, respectively, for patients with latent obstruction compared with 93% and 74%, respectively, for patients with severe resting obstruction preoperatively (P = .34). Self-reported late functional status was similar; 3 to 5 years postoperatively, 81% of patients with latent obstruction preoperatively were in New York Heart Association class I or II compared with 77% of patients with severe resting obstruction. Patients with obstructive hypertrophic cardiomyopathy who have low resting gradients and latent obstruction may have limiting symptoms comparable to those of patients with more severe resting gradients. Septal myectomy should be offered to these patients because survival and symptom relief are excellent, suggesting that dynamic obstruction is the major hemodynamic problem rather than diastolic dysfunction.

A comparison of pharmacologic and spontaneous baroreflex methods in aging and hypertension

Phenylephrine bolus injection is an established technique to measure baroreflex sensitivity (BRS). This study quantified the relationship between the phenylephrine method and noninvasive measures of BRS and examined the effects of aging and hypertension on BRS. We also examined whether heart rate variability (HRV) provides as much information as does BRS. BRS was determined by phenylephrine bolus (BRSphe), amyl nitrite inhalation (BRSamyl), Valsalva maneuver (BRSVals) and by time (BRS(+)) and spectral domain analysis (BRS(LFalpha), 004-015 Hz) of spontaneous blood pressure and R-R interval changes over the 5-min time period. The phenylephrine method significantly correlated with other methods (BRS(LFalpha) R = 0.54, BRS(+) R = 0.55, BRSVals R = 0.43 and BRSamyl R = 0.39; P < or = 0.001). Each method underestimated the BRSphe by the factors 0.62, 0.64, 0.59 and 0.33, respectively; P value less than 0.001. Only BRS(LFalpha) was significantly different between normotensive and hypertensive patients in young [24.3 +/- 1.4 (n = 40) vs. 12.2 +/- 2.3 (n = 7)] and middle-aged [16.5 +/- 1.1 (n = 71) vs. 10.8 +/- 1.1 (n = 31) groups, respectively]. HRV in the high frequency band (0.15-0.40 Hz) was significantly lower in young hypertensive patients than in normal controls (26 +/- 6.0 vs. 50 +/- 2.4, P < 0.05). Although all methods correlated with the phenylephrine technique, none of them could be used interchangeably with that technique. BRS(LFalpha) detected the baroreflex loss of hypertension most clearly, and BRSamyl did not differ among groups.

Inhaled amyl nitrite effectively reverses acute catastrophic thromboxane-mediated pulmonary hypertension in pigs

Acute catastrophic pulmonary vasoconstriction frequently leads to cardiovascular collapse. Rapid and selective pulmonary vasodilation is desired in order to restore haemodynamic stability. This pilot study examined the effectiveness of inhaled amyl nitrite as a selective pulmonary vasodilator. Nine adult swine were anaesthetized. Acute pulmonary hypertension with haemodynamic collapse was induced with a bolus administration of a thromboxane analogue, U46619. Six animals then received a capsule of amyl nitrite. The administration of inhaled amyl nitrite decreased mean pulmonary artery pressure from 42 +/- 3 to 22 +/ 3 mmHg at five minutes (p < 0.05), with a concomitant increase in cardiac output and mean arterial pressure. Pulmonary vascular resistance decreased from 4889 +/- 1338 to 380 +/- 195 dyne. sec. cm(-5) (by 92% from the maximal pulmonary hypertension change), with significant improvement in systemic haemodynamics. During acute thromboxane-mediated pulmonary hypertension with cardiovascular collapse, prompt administration of inhaled amyl nitrite was effective in restoring pulmonary and systemic haemodynamics within five minutes.

Comparative effects of glyceryl trinitrate and amyl nitrite on pulse wave reflection and augmentation index

The influence of vasodilators on augmentation index (AIx) offers a simple, rapid and noninvasive method of evaluating vascular function. Glyceryl trinitrate (GTN) is widely used as an endothelium-independent vasodilator, although other nitrates that are shorter acting may have advantages in clinical studies. The aim of this study was to compare the effects of two short-acting nitrates, GTN and amyl nitrite, which have differing pharmacodynamic profiles. Twenty-one healthy volunteers (15 male; mean age 35 years, range 21-56 years) attended on three occasions and received sublingual GTN (0.5 mg for 3 min), inhaled amyl nitrite (0.2 ml inhaled for 30 s), or no treatment in a randomized cross-over design. Haemodynamic responses of AIx, blood pressure and thoracic bioimpedance (heart rate, cardiac index) were assessed by measurement at baseline, every 60 s for the first 5 min, and then every 5 min for a further 55 min. AIx was reduced by amyl nitrite (peak effect -9 +/- 2% at 1 min, P < 0.002) and GTN (peak effect -12 +/- 3% at 4 min, P < 0.05). Compared with amyl nitrite, the onset and offset of action of GTN was slower. Amyl nitrite initially increased heart rate by 27 +/- 4% (P < 0.001) and cardiac index by 13 +/- 3% (P < 0.001) whereas GTN had no significant effect (P > 0.05). Neither agent affected blood pressure. GTN causes a slower and more sustained reduction in AIx than amyl nitrite. Although amyl nitrite causes a more rapid fall and recovery in AIx, it induces a reflex tachycardia that may limit interpretation of the initial (1 min) but not later (2 min) changes in AIx. The prolonged offset of GTN suggests that a sufficient washout period must be included when making repeated measures or when assessing the subsequent effects of other agents.

Acute haemolytic anaemia after inhalation of amyl nitrite

commonly misdiagnosed—especially as melanocytic naevus, basal cell carcinoma, seborrhoeic keratosis or lentigo.5 In a study comparing the ability of general practitioners and dermatologists to discriminate pigmented lesions the general practitioners made an exact diagnosis of melanoma in 50% of the cases compared with the dermatologists’ 84%.6 Any changing or atypical mole or non-healing skin lesion should be referred urgently to a dermatologist or to a surgeon with a special interest in pigmented lesions.

Color M-Mode Doppler Flow Propagation Velocity Is a Relatively Preload-Independent Index of Left Ventricular Filling

Standard Doppler indexes of transmitral filling vary in response to alterations in left ventricular (LV) relaxation or preload. To determine whether color M-mode Doppler flow propagation velocity (v p ), a new index of LV relaxation, is affected by preload, we obtained LV volumes, standard Doppler filling indexes, and v p in 20 patients at baseline, during Trendelenburg’s position, inverse Trendelenburg’s position, and after inhalation of amyl nitrite. LV end-diastolic volume decreased from 111 ± 41 mL at baseline and 116 ± 43 mL during Trendelenburg’s position, to 104 ± 40 during inverse Trendelenburg’s maneuver and 92 ± 33 mL after inhalation of amyl nitrite ( P < .0001). Peak early filling velocity decreased from 79 ± 19 cm/s and 90 ± 20 cm/s to 73 ± 22 cm/s and 64 ± 20 cm/s, respectively ( P < 0.0001). In contrast, no significant changes were found in v p (48 ± 24 and 50 ± 26 cm/s vs 48 ± 25 and 48 ± 25 cm/s). We conclude that v p is not affected significantly by preload. Thus v p may provide a more reliable and independent assessment of LV relaxation. (J Am Soc Echocardiogr 1999;12:129-37.)

A case of methemoglobinemia after ingestion of an aphrodisiac, later proven as dapsone

Methemoglobin (MetHb) is an oxidation product of hemoglobin in which the sixth coordination position of ferric iron is bound to a water molecule or to a hydroxyl group. The most common cause of acquired MetHb-emia is accidental poisoning which usually is the result of ingestion of water containing nitrates or food containing nitrite, and sometimes the inhalation or ingestion of butyl or amyl nitrite used as an aphrodisiac. We herein report a case of MetHb-emia after ingestion of an aphrodisiac, later identified as dapsone by gas chromatograph/mass selective detector (GC/MSD). A 24-year old male was admitted due to cyanosis after ingestion of a drug purchased as an aphrodisiac. On arterial blood gas analysis, pH was 7.32, PaCO2 26.8 mmHg, PaO2 75.6 mmHg, and bicarbonate 13.9 mmol/L. Initial pulse oxymetry was 89%. With 3 liter of nasal oxygen supplement, oxygen saturation was increased to 90-92%, but cyanosis did not disappear. Despite continuous supplement of oxygen, cyanosis was not improved. On the fifth hospital day, MetHb was 24.9%. Methylene blue was administered (2 mg/kg intravenously) and the patient rapidly improved. We proved the composition of aphrodisiac as dapsone by the method of GC/MSD.

Oesophageal tone in patients with achalasia

Background—The diagnosis and classification of oesophageal motility disorders is currently based on assessment of the phasic contractile activity of the oesophagus. Tonic muscular contraction of the oesophageal body (oesophageal tone)...

Subaortic septal bulge simulates hypertrophic cardiomyopathy by angulation of the septum with age, independent of focal hypertrophy. An echocardiographic study

Focal hypertrophy of the basal anterior septum occurs not infrequently in elderly patients and is considered by some to be a significant form of hypertrophic cardiomyopathy; others consider it to be an unimportant anatomic variant associated with an angulated septum, called a septal bulge (SB). We analyzed 94 cases of SB collected prospectively and compared them with 88 patients with extensive hypertrophic cardiomyopathy (≤CM), 20 patients with hypertrophic cardiomyopathy limited to the entire septum (ASH), and 20 age-matched controls. The SB cases were also divided into three groups, with marked, moderate, or no basal septal hypertrophy associated with the occurrence of an SB. All groups of SB patients had increased fractional shortening compared with controls (0.48 ± 0.07 versus controls 0.40 ± 0.07), comparable with HCM (0.48 ± 0.12), and increased left ventricular outflow tract velocity both at rest and especially after amyl nitrite inhalation (3.42 ± 1.35 versus 1.55 ± 0.60 m/sec [controls]). Other features of HCM were not present: normal wall thickness except for the basal septal hypertrophy, no anterior malposition in SB patients, no age-independent reversal of ratio of early to late mitral inflow velocity (E/A), and no decrease in end-diastolic dimension. It is concluded that outflow tract narrowing by an angulated septum is the primary mechanism responsible for the increased outflow tract velocity, rather than the hypertrophic septum. The resultant increase in convective acceleration simulates the dynamics of hypertrophic cardiomyopathy. The focal hypertrophy may be secondary and contributory to the enhanced ventricular dynamics, but it does not appear to be a primary cardiomyopathy. (J Am Soc Echocardiogr 1997;10:545-55.)

Resting Echocardiographic Features of Latent Left Ventricular Outflow Obstruction in Hypertrophic Cardiomyopathy

We determined resting echocardiographic features predictive of latent left ventricular (LV) outflow obstruction in 50 consecutive patients with nonobstructive hypertrophic cardiomyopathy (26 provocable, 24 nonprovocable with amyl nitrite inhalation) to have a better understanding of the pathophysiology of this condition and to identify such patients without pharmacologic provocation. Measurements included wall thickness, type of hypertrophy, LV outflow tract diameter, degree of mitral systolic anterior motion, outflow pressure gradient, and ventricular volume. The direction of the ejection streamline was measured to assess the magnitude of the drag force acting on the mitral valve. Thirteen of 16 patients (81%) with proximal septal bulge were provocable, whereas only 3 of 8 patients (38%) with asymmetric septal hypertrophy and 10 of 26 (38%) with concentric hypertrophy were provocable (p <0.05). LV outflow tract was significantly narrower and the angle between the ejection flow and the mitral valve was larger in provocable patients. The sensitivity for predicting provocable patients by a combination of a narrow outflow tract (≤2 cm) and a large angle ( ≥35°) was 65%, with a specificity of 80% and a positive predictive value of 79%. When these criteria were combined with the presence of septal bulge, the sensitivity was 35%, but the specificity and the positive predictive value were both 100%. Patients with nonobstructive hypertrophic cardiomyopathy with proximal septal bulge, a narrow LV outflow tract, and an oblique angle between the ejection flow and the mitral valve appeared to be predisposed for latent outflow obstruction. These features are consistent with the presence of the large Venturi and drag forces. Thus, the left ventricle, which is capable of increasing both the Venturi and the drag forces on the basis of the morphologic change, contributes to the development of outflow obstruction with amyl nitrite inhalation.(Am J Cardiol 1996;78:622–667)

Clinical significance of the apical late systolic ejection murmur: a new phonocardiographic sign indicating dynamic mid-left ventricular obstruction.

Systolic ejection murmurs of the left heart usually have their peak during early to mid-systole. Few reports have addressed ejection murmurs with their peak at late systole. We evaluated the clinical significance of an apical systolic ejection murmur with a peak intensity during late systole using Doppler and two-dimensional (2-D) echocardiography and phonocardiography. The apical late systolic ejection murmur was observed in 9 of 13 consecutive patients with mid-left ventricular obstruction. We investigated the ejection flow velocity and the timing of maximum velocity at the three different sites of the left ventricle, the left ventricular cavity shape, and the timing of the peak murmur intensity in these nine patients (late-murmur group). The same parameters were also examined in 8 consecutive patients with mid-systolic ejection murmurs (mid-murmur group), 10 with early systolic ejection murmurs (early-murmur group), and 7 controls without murmurs. Patients with aortic stenosis were excluded. The mid-ventricular ejection flow velocity was significantly higher in the late-murmur group than in the other three groups; that of the outflow tract was markedly higher in the mid-murmur group. The ejection flow velocity at the aortic orifice of patients in the early-murmur group was significantly high compared with that of the controls. The timing of the peak murmur intensity in each group correlated with that of the peak flow signal at the corresponding site with maximum velocity. In all patients in the late-murmur group, 2-D echocardiography revealed a systolic narrowing of the cavity at the mid-ventricle. Amyl nitrite inhalation induced a marked increase in the intensity of the murmur without evidence of appearing or increasing mitral regurgitation. It was concluded that the apical ejection murmur with a late systolic peak intensity is a new phonocardiographic sign indicative of dynamic, mid-left ventricular obstruction. This murmur should be differentiated from the mitral regurgitant murmur.

Transesophageal Echocardiographic Analysis of the Systolic Pattern of the Anterior Mitral Leaflet in Patients with Flat Chest

Transesophageal echocardiography was conducted to determine the systolic pattern of the anterior mitral leaflet in patients with flat chest, and to differentiate it from that associated with mitral valve prolapse. The fronto‐sagittal index (an index of chest flattening) was determined in 50 subjects using chest radiographs, and was used to classify them into a flat chest group (index &lt; 0.38, n= 28) and a normal chest group (index ≥ 0.38, n= 22). We then used transesophageal echocardiography to examine the anterior leaflet in these subjects. A significant positive correlation was observed between the fronto‐sagittal index and the short‐to long‐axis diameter ratio of the left ventricle in all patients. These parameters, and the left atrial dimension were lower in the flat than the normal chest group. The clear zone area of the anterior leaflet during mid‐to late‐systole was significantly larger in the flat chest group. However, no intergroup differences existed in the rough zone area of the anterior leaflet or in the middle scallop area of the posterior leaflet. Mitral regurgitation was observed in 20 and 12 subjects in the flat and normal chest groups, respectively. The maximum mitral regurgitant area did not differ between the two groups. The clear zone area of the anterior leaflet increased significantly following inhalation of amyl nitrite in 22 subjects of both groups, but the other areas did not increase. The mitral regurgitant area decreased or disappeared after amyl nitrite at a similar rate in each group. Thus, the decrease in the antero‐posterior dimension of the thorax in subjects with flat chest affects the systolic pattern of the clear zone of the anterior leaflet more than that of the rough zone of the anterior leaflet or the posterior leaflet. This systolic pattern in such patients differs from that associated with mitral valve prolapse.

Provocation of latent left ventricular outflow tract gradients with amyl nitrite and exercise in hypertrophic cardiomyopathy

Amyl nitrite may be used to provoke latent gradients in patients with hypertrophic cardiomyopathy (HC) without significant resting outflow tract gradients, but afterload reduction may not be comparable to a more physiologic Stressor such as symptom-limited exercise testing. This study compared the ability of amyl nitrite and exercise testing to provoke outflow tract gradients in 57 patients (40 men and 17 women, mean age ± SD 49 ± 16 years) with HC (septal thickness 19 ± 5 mm, average resting gradient 13 ± 10 mm Hg) who underwent echocardiography at rest, after amyl nitrite inhalation, and after maximal exercise. No significant gradient (< 50 mm Hg) was induced after either provocation in 26 patients (46%); in 15 patients (26%), inducibility was achieved after both stressors, in 6 (11%) after exercise only, and in 10 (18%) after amyl only. Patients with amyl-induced gradients differed from those in whom gradients were noninducible on the basis of smaller outflow tract dimensions (p < 0.001), larger resting gradients (p < 0.001), and a greater prevalence of “septal bulge” morphology (p = 0.02). Those with exercise-induced gradients were able to attain a greater workload (p = 0.07), have larger resting gradients (p = 0.02), and also tended to have a septal bulge morphology (p ≤0.01). Although outflow tract obstruction increased to similar levels after amyl nitrite (49 ± 39 mm Hg) and symptom-limited exercise (47 ± 39 mm Hg), gradients induced by exercise and amyl correlated poorly (r = 0.54). Gradients were the same (within 10%) with both stressors in 14 patients (25%), greater with exercise in 25 (44%), and greater with amyl in 18 patients (32%). Measurement of outflow tract gradients after exercise should be included in the assessment of patients with HC with suspected latent outflow obstruction, particularly in younger patients without amyl-induced outflow tract gradients.

763-4 Resting Echocardiography Identifies Hypertrophic Cardiomyopathy Patients with Latent Left Ventricular Outflow Obstruction

Latent LV outflow tract (OT) obstruction has important therapeutic and prognostic implications in patients with hypertrophic cardiomyopathy (HCM). However, since its presence can not be known until it is provoked, we investigated the resting echo features of patients with latent LVOT obstruction, aiming to predict it before provocation. 48 patients with non-obstructive HCM (resting LVOT pressure gradient (PG) &lt; 40 mmHg) challenged with amyl nitrite inhalation were studied. 23 patients (mean 51 ± 18 years) were nonprovocable and 25 (mean 52 ± 12 years, p = ns) were provocable (LVOT-PG ≥ 40 mmHg with amyl). Echo measurements included assessment of LV shape (asymmetric septal hypertrophy (ASH), concentric hypertrophy (CH) and prominent basal septal bulge (SB), anterior and posterior mitral leaflet length, qualitative assessment of mitral valve systolic anterior motion (SAM, 0 = none to 3 = severe), LVOT-PG, LVOT diameter at the onset of systole (DlA, cm), septal and posterior wall thickness, end-diastolic and end-systolic volume, and ejection fraction determined by Simpson's method. The angle (α, degrees) between the color Doppler-determined ejection streamline in LVOT and the LV long axis was measured to assess the magnitude of the drag force acting on the mitral valve. 12 of 16 patients (80%) with SB showed LVOT obstruction after amyl inhalation, whereas only 3 of 8 patients (38%) with ASH and 10 of 25 (40%) with CH showed obstruction (p &lt; 0.05). Unpaired t-testing revealed the following: SAM resting PG DIA α nonprovocable 0.5 ± 0.8 9 ± 4 2.2 ± 03 32 ± 9 provocable 0.9 ± 09 13 ± 9 1.8 ± 03 37 ± 7 p value 0.11 0.06 &lt; 0.0001 &lt; 0.05 The sensitivity for predicting provocable patients by combination of small LVOT diameter (≤2 cm) and large α (≥ 35 degrees) was 64% and the specificity was 79%. Wall thickness, leaflet length, ventricular volume, and ejection fraction did not show significant differences between two groups. Multiple stepwise linear regression analysis showed DIA and resting PG are best predictors for PG after amyl inhalation (r = 0.67, p &lt; 0.001). Non-obstructive HCM patients with 1) prominent septal bulge, 2) narrow LVOT, 3) oblique angle between the ejection flow and the LV long-axis, and 4) higher resting PG appeared to be predisposed for latent LVOT obstruction.

763-5 Provocation of Latent Left Ventricular Outflow Tract Gradients with Amyl Nitrite and Exercise in Patients with Hypertrophic Cardiomyopathy

In pts with hypertrophic cardiomyopathy (HCM) who have obstructive symptoms without significant resting outflow tract gradients, amyl nitrite may be used to provoke latent obstruction. However, the provocative effect of afterload reduction may not be comparable to a more physiologic method such as symptom-limited exercise stress testing. This study compared the ability of amyl nitrite and exercise testing to provoke outflow tract gradients in the same pts. Sixty-one pts (age 49 ± 17y, 43 male) with non-obstructive HCM (septal thickness 19 ± 5 mm, resting outflow tract gradient 15 ± 14 mmHg) underwent echocardiography at rest, following amyl nitrite inhalation, and after maximal exercise. Twenty-six pts (43%) remained without significant inducible gradients «50 mmHg) after either provocation, 17 (28%) became inducible after both stressors, 7 (11%) after exercise only, and 11 (18%) after amyl only. Although obstruction increased to similar levels after amyl nitrite (50 ± 38 mmHg) and after symptom-limited exercise (49 ± 39 mmHg), gradients induced by exercise and amyl correlated poorly (r = 0.54). Gradients were the same with both stressors in 15 patients (EO group), greater with exercise in 26 (EX group), and greater with amyl in 20 patients (AM group). Differences between amyl and exercise were unrelated to drug therapy. EQ(n = 15) EX(n = 26) AM (n = 20) p Age (ys) 37 ± 15 47 ± 17 61 ± 9 p &lt; 0.001 EQ vs AM Septum (mm) 21 ± 5 20 ± 6 17 ± 3 p &lt; 0.01 EQ vs AM Ex HR (% predicted) 73 ± 23 96 ± 9 82 ± 16 p &lt; 0.001 EQ vs EX Exercise RPP (× 10 3 ) 21.4±8.2 33.9 ± 7.7 24.3 ± 85 p &lt; 0.001 EQ vs EX Amyl gradient (mmHg) 40 ± 39 37 ± 33 76 ± 34 p &lt; 0.001 EQ vs AM Ex gradient (mmHg) 40 ± 39 67 ± 42 33 ± 25 p &lt; 0.03 EQ vs EX Over 50% of pts with non-obstructive HCM at rest have inducible gradients which may explain inlermittent symptoms. Measurement of gradients after AM and EX should be included in the assessment of pts with HCM with suspected latent outflow obstruction. Pts with a preponderant AM response are older and have less hypertrophy. EX is particularly indicated in younger patients without AM-induced gradients.

916-90 Is Baroreflex Failure Different from Idiopathic Baroreceptor Dysfunction?

Baroreflex failure (BRF) due to local causes was reported as a syndrome of labile hypertension, exaggerated response to cold pressor test (CPT) and elevated plasma catecholamines. We hypothesized that the pattern of autonomic abnormalities is different in the idiopathic type of BR dysfunction (BRD). Twenty four subjects (13 M: 11 F; age 62 ± 16 yrs.) with tilt-induced orthostatic hypotension (OH) were tested for: Valsalva, CPT, baroreflex sensitivity (heart rate response to acute BP alteration using Phenylephrine [PE] and amylnitrite inhalation [ANI]. BRD was diagnosed by blocked Valsalva, abnormal PE and/or AN. Two groups were defined by the results of BR and tilt; 19 with BRD (OH-BRD) and 5 with normal BR (OH-NBR). They were compared to results in 31 control subjects (19 M: 12 F; age 40 ± 15 yrs.) who had normal tilt and normal BR (N-NBR). Plasma Norepinephrine (NE) was determined in supine and tilt positions. Tilt Δ(SBP) CPT Δ(SBP) AN (Slope) PE (Slope) Tilt (ΔNE) 1. OH-BRD -63 ± 21 * 22 ± 9 * 0.0 ± 06 *† 0.4 ± 1 † 15.4 ± 21.6 2.0H-NBR -36 ± 11 ‡ 34 ± 10 3.8 ± 24 8.8 ± 3 28.4 ± 17.0 3. NL-NBR -6 ± 8 29 ± 15 4.2 ± 29 7.5 ± 7 24.6 ± 18.9 X ± SD, P &lt; 0.017 * 1 vs 3 † vs 2 ‡ 2vs 3 (1) Patients with idiopathic BRD present with OH, have attenuated response to CPT and normal catecholamine response to tilt. (2) OH-BRD and BRF are two different syndromes with different etiologies and clinical manifestations; however, both have BR abnormalities.