Low-flow, low-gradient aortic stenosis: from evaluation to treatment

PURPOSE OF REVIEW

Valve replacement improves symptoms and survival in symptomatic severe aortic stenosis. Low-flow, low-gradient aortic stenosis, however, is an especially challenging subset as valve replacement has a significant risk, and may fail to alleviate symptoms or improve left ventricular function. This article reviews the potential problems in evaluating aortic stenosis severity in low-flow, low-gradient aortic stenosis, the utility of dobutamine challenge to identify patients most likely to benefit from surgery, and the factors predicting patient outcome.

RECENT FINDINGS

Low-flow, low-gradient aortic stenosis consists of a heterogeneous group of patients with 'true' severe aortic stenosis, in whom afterload mismatch results from a severely stenotic valve; and 'pseudo-severe' aortic stenosis, where the valve is only mildly or moderately stenotic, but appears severe due to limitations in determining disease severity under low-flow conditions. Valve replacement is likely to benefit the former group, but may have little benefit to the latter. Dobutamine challenge can distinguish 'true' and 'pseudo-severe' aortic stenosis, and can evaluate contractile reserve, one of the strongest predictors of patient outcome. Strategies to avoid prosthesis-patient mismatch should be considered to optimize postoperative outcome.

SUMMARY

Dobutamine challenge can identify low-flow, low-gradient aortic stenosis patients most likely to benefit from valve replacement and provides important prognostic information on the operative risks and long-term outcome.

The Effects of Continuous Positive Airway Pressure on Myocardial Energetics in Patients With Heart Failure and Obstructive Sleep Apnea

OBJECTIVES

We sought to examine the short-term and longer term (6-week) effects of continuous positive airway pressure (CPAP) on myocardial energetics.

BACKGROUND

Obstructive sleep apnea (OSA) and heart failure (HF) are both states of increased afterload and metabolic demand. Treatment with CPAP may initially reduce stroke volume but subsequently improves left ventricular function. However, it is not clear whether CPAP therapy favorably affects myocardial energetics and hence improves cardiac efficiency.

METHODS

Twelve patients with HF were divided into two groups: 7 patients with OSA were treated with CPAP (group I), and 5 patients without OSA served as a control group (group II). Oxidative metabolism was measured using the mono-exponential fit of the myocardial [(11)C] acetate positron emission tomography time-activity curve (k-mono). Myocardial efficiency was derived using the work metabolic index (WMI = [heart rate x stroke volume index x systolic blood pressure]/k-mono) measured at baseline, during short-term CPAP, and after 6 +/- 3 weeks of CPAP.

RESULTS

In group I, short-term CPAP tended to reduce SVI (p = 0.063) and reduced oxidative metabolism (p = 0.031). Work metabolic index did not change. However, longer term CPAP improved left ventricular ejection fraction (38.4 +/- 3.3% to 43.4 +/- 4.8%, p = 0.031), tended to reduce oxidative metabolism (0.047 +/- 0.012 to 0.040 +/- 0.008 min(-1), p = 0.078), and improved WMI (7.13 +/- 2.82 x 10(6) to 8.17 +/- 3.06 x 10(6) mm Hg.ml/m(2), p = 0.031). In group II (control), these parameters did not change.

CONCLUSIONS

In this cohort of patients with HF and OSA, short-term CPAP decreased oxidative metabolism and tended to decrease SVI, but did not alter cardiac efficiency. Longer term CPAP improved cardiac efficiency, indicating an energy-sparing effect. These effects may contribute to the benefits of CPAP therapy.

Cardiac Actinomycosis: An Unusual Cause of an Intracardiac Mass

Actinomycosis is a chronic disease characterized by abscess formation, tissue fibrosis, and draining sinuses that may involve the cervicofacial area, thorax, abdominopelvic region, or central nervous system. We describe a patient with cardiac actinomycosis presenting with pericardial disease and an intracardiac mass. The diagnosis failed to be obtained by pericardiocentesis, but was obtained after echocardiographically guided biopsy of the intracardiac mass. The patient recovered with long-term penicillin therapy. A review of the literature highlights the frequent pericardial presentation of cardiac actinomycosis, the potential difficulty in making the diagnosis, and the remarkable clinical response and good prognosis that can result when the correct diagnosis is made and appropriate antibiotic therapy administered.

Impact of blood pressure on the Doppler echocardiographic assessment of severity of aortic stenosis

OBJECTIVE

To investigate the impact of blood pressure (BP) on the Doppler echocardiographic (Doppler-echo) evaluation of severity of aortic stenosis (AS).

METHODS

Handgrip exercise or phenylephrine infusion was used to increase BP in 22 patients with AS. Indices of AS severity (mean pressure gradient (DeltaP(mean)), aortic valve area (AVA), valve resistance, percentage left ventricular stroke work loss (% LVSW loss) and the energy loss coefficient (ELCo)) were measured at baseline, peak BP intervention and recovery.

RESULTS

From baseline to peak intervention, mean (SD) BP increased (99 (8) vs 121 (10) mm Hg, p<0.001), systemic vascular resistance (SVR) increased (1294 (264) vs 1552 (372) dynexs/cm(5), p<0.001) and mean (SD) transvalvular flow rate (Q(mean)) decreased (323 (67) vs 306 (66) ml/s, p = 0.02). There was no change in DeltaP(mean) (36 (13) vs 36 (14) mm Hg, p = NS). However, there was a decrease in AVA (1.15 (0.32) vs 1.09 (0.33) cm(2), p = 0.02) and ELCo (1.32 (0.40) vs 1.24 (0.42) cm(2), p = 0.04), and an increase in valve resistance (153 (63) vs 164 (74) dynexs/cm(5), p = 0.02), suggesting a more severe valve stenosis. In contrast, % LVSW loss decreased (19.8 (6) vs 16.5 (6)%, p<0.001), suggesting a less severe valve stenosis. There was an inverse relationship between the change in mean BP and AVA (r = -0.34, p = 0.02); however, only the change in Q(mean) was an independent predictor of the change in AVA (r = 0.81, p<0.001).

CONCLUSIONS

Acute BP elevation due to increased SVR can affect the Doppler-echo evaluation of AS severity. However, the impact of BP on the assessment of AS severity depends primarily on the associated change in Q(mean), rather than on an independent effect of SVR or arterial compliance, and can result in a valve appearing either more or less stenotic depending on the direction and magnitude of the change in Q(mean).

Long-term outcomes after valve replacement for low-gradient aortic stenosis: impact of prosthesis-patient mismatch

BACKGROUND

The long-term outcomes of patients with low-gradient aortic stenosis (LGAS) after aortic valve replacement (AVR) are poorly defined. The purpose of this study was to define the long-term outcomes of LGAS patients after AVR and to evaluate the potential impact of prosthesis-patient mismatch (PPM) in these patients.

METHODS AND RESULTS

A cohort of 664 patients undergoing AVR for aortic stenosis after 1990 were followed-up prospectively with annual clinical assessment and echocardiography (total follow-up 3447 patient-years; mean follow-up 5.2+/-3.3 years). LGAS was defined as an aortic valve area <1.2 cm2, a mean transvalvular pressure gradient <40 mm Hg, and a left ventricular (LV) ejection fraction <50%, and was present in 79 patients. Rates and correlates of survival, freedom from congestive heart failure (CHF), and LV mass regression after AVR were determined using multivariate regression methods. Ten-year survival and freedom from CHF after AVR were 72.7+/-7.5% and 68.2+/-9.5%, respectively, for patients with LGAS, compared with 89.6+/-1.8% and 84.1+/-4.2% for patients without LGAS (hazard ratio [HR] for death and postoperative CHF, 3.1+/-1.1 and 2.7+/-0.9, respectively; P<0.01). In LGAS patients, PPM, defined as an indexed effective orifice area < or = 0.85 cm2/m2, was independently associated with increased rates of CHF (HR, 3.6+/-2.2; P=0.039), impaired LV mass regression (P=0.037), and a trend toward increased late mortality (HR, 3.0+/-1.9; P=0.084).

CONCLUSIONS

Patients with LGAS have worse long-term outcomes after AVR compared with patients without LGAS. PPM adversely affects the long-term outcomes of LGAS patients and should be avoided in this population.

Natural History and Predictors of Outcome in Patients With Concomitant Functional Mitral Regurgitation at the Time of Aortic Valve Replacement

BACKGROUND

Concomitant functional mitral regurgitation (FMR) in patients undergoing aortic valve replacement (AVR) is frequently not corrected because it may improve after AVR; however, data supporting this assumption are sparse. We ascertained the impact of clinical and echocardiographic parameters on the outcome of patients with or without concomitant FMR at the time of AVR.

METHODS AND RESULTS

Clinical and echocardiographic follow-up was performed on 848 patients who underwent AVR after 1990. Risk factors for mortality and a composite outcome of heart failure (CHF) symptoms, CHF death, or subsequent mitral repair or replacement, were examined with bootstrapped Cox proportional hazard models. Follow-up was 4591 patient-years (mean 5.4+/-3.4 years; maximum 14.2 years). FMR > or = 2+ had no independent adverse effect on survival in patients with aortic stenosis (AS) or insufficiency (AI). However, AS patients with FMR > or = 2+ and 1 additional risk factor (left atrial diameter >5 cm, preoperative peak aortic valve gradient <60 mm Hg, or atrial fibrillation) were at increased risk for the composite outcome (hazard ratio [HR]: 2.7; P=0.004). AI patients with FMR > or = 2+ and a left ventricular end-systolic diameter <45 mm were also at risk (HR: 4.0; P=0.02). Clinical risk factors in the AS and AI subgroups were associated with an increased likelihood of mitral regurgitation > or = 2+ at 18 months postoperatively.

CONCLUSIONS

AS patients with FMR > or = 2+ and a left atrial diameter >5 cm, preoperative peak aortic valve gradient <60 mm Hg, or atrial fibrillation have a significantly higher risk of CHF and persistent mitral regurgitation after AVR than other AS patients. AI patients with FMR > or = 2+ and a left ventricular end-systolic diameter <45 mm preoperatively are also at increased risk. Others fare well after AVR.

Prosthesis–patient mismatch after aortic valve replacement predominantly affects patients with preexisting left ventricular dysfunction: Effect on survival, freedom from heart failure, and left ventricular mass regression

OBJECTIVE

The effect of prosthesis-patient mismatch on clinical outcome and left ventricular mass regression after aortic valve replacement remains controversial. Data on whether the clinical effect of prosthesis-patient mismatch depends on left ventricular function at the time of aortic valve replacement are lacking. This study examined the long-term clinical and echocardiographic effects of prosthesis-patient mismatch in patients with and without left ventricular systolic dysfunction at the time of aortic valve replacement.

METHODS

Preoperative and serial postoperative echocardiograms were performed in 805 adults who underwent aortic valve replacement between 1990 and 2003 and who were subsequently followed up in a dedicated valve clinic (follow-up, mean +/- SD, 5.5 +/- 3.5 years; maximum, 14.2 years). Preoperative left ventricular function was defined as normal (ejection fraction > or =50%) in 548 patients and impaired (ejection fraction <50%) in 257 patients.

RESULTS

Patients with impaired preoperative left ventricular function and prosthesis-patient mismatch (indexed effective orifice area < or =0.85 cm2/m2) had a decreased overall late survival (hazard ratio, 2.8; P = .03), decreased freedom from heart failure symptoms or heart failure death (odds ratio of 5.1 at 3 years after aortic valve replacement; P = .009), and diminished left ventricular mass regression compared with patients with impaired preoperative left ventricular function and no prosthesis-patient mismatch. These effects of prosthesis-patient mismatch were not observed in patients with normal preoperative left ventricular function.

CONCLUSIONS

Prosthesis-patient mismatch at an indexed effective orifice area of 0.85 cm2/m2 or less after aortic valve replacement primarily affects patients with impaired preoperative left ventricular function and results in decreased survival, lower freedom from heart failure, and incomplete left ventricular mass regression. Patients with impaired left ventricular function represent a critical population in whom prosthesis-patient mismatch should be avoided at the time of aortic valve replacement.

Projected valve area at normal flow rate improves the assessment of stenosis severity in patients with low-flow, low-gradient aortic stenosis: the multicenter TOPAS (Truly or Pseudo-Severe Aortic Stenosis) study

BACKGROUND

We sought to investigate the use of a new parameter, the projected effective orifice area (EOAproj) at normal transvalvular flow rate (250 mL/s), to better differentiate between truly severe (TS) and pseudo-severe (PS) aortic stenosis (AS) during dobutamine stress echocardiography (DSE). Changes in various parameters of stenosis severity have been used to differentiate between TS and PS AS during DSE. However, the magnitude of these changes lacks standardization because they are dependent on the variable magnitude of the transvalvular flow change occurring during DSE.

METHODS AND RESULTS

The use of EOAproj to differentiate TS from PS AS was investigated in an in vitro model and in 23 patients with low-flow AS (indexed EOA <0.6 cm2/m2, left ventricular ejection fraction < or =40%) undergoing DSE and subsequent aortic valve replacement. For an individual valve, EOA was plotted against transvalvular flow (Q) at each dobutamine stage, and valve compliance (VC) was derived as the slope of the regression line fitted to the EOA versus Q plot; EOAproj was calculated as EOAproj=EOArest+VCx(250-Q(rest)), where EOArest and Q(rest) are the EOA and Q at rest. Classification between TS and PS was based on either response to flow increase (in vitro) or visual inspection at surgery (in vivo). EOAproj was the most accurate parameter in differentiating between TS and PS both in vitro and in vivo. In vivo, 15 of 23 patients (65%) had TS and 8 of 23 (35%) had PS. The percentage of correct classification was 83% for EOAproj and 91% for indexed EOAproj compared with percentages of 61% to 74% for the other echocardiographic parameters usually used for this purpose.

CONCLUSIONS

EOAproj provides a standardized evaluation of AS severity with DSE and improves the diagnostic accuracy for distinguishing TS and PS AS in patients with low-flow, low-gradient AS.

Retained Left Atrial Catheter: A Case Report and Review of the Literature

We describe a patient in whom transesophageal echocardiography detected a portion of retained left atrial catheter that had been left in situ for 21 years after aortic valve replacement. Although thrombus was present on the catheter, the patient had no history of systemic embolization, potentially as a result of the use of chronic anticoagulation with warfarin. A review of the literature identified 8 previous cases of a retained left atrial catheter. Retained left atrial catheters can be easily detected with transesophageal echocardiography and appear to have a significant risk of thrombus formation and systemic embolization that warrants removal of the catheter when identified.

Comparison of real-time 3-dimensional echocardiography with conventional 2-dimensional echocardiography in the assessment of structural heart disease

We evaluated the diagnostic use of a real-time 3-dimensional (3D) echocardiographic system in 106 patients referred for echocardiography during a 4-month period. Real-time 3D echocardiography was performed and recorded in parallel with a routine, comprehensive 2-dimensional (2D) study. The diagnoses were exclusively on the basis of 2D findings. The 3D volumes were sliced offline in the 3 dimensions to selectively display specific cardiac structures and reviewed independent of the 2D findings. The 3D studies were graded as: A, new finding not on 2D studies; B, useful anatomic perspective; C, equivalent to 2D studies; or D, missed 2D findings. Compared with 2D echocardiography, 3D echocardiography was graded A in 7 (7%), B in 19 (18%), C in 65 (61%), and D in 15 (14%) cases. In the 26 grade-A and grade-B studies, mitral valve disease and congenital heart disease accounted for 16 (61%) cases. Suboptimal image quality was present in 7 (47%) of the 15 grade-D studies. Thus, real-time 3D echocardiography yields anatomic information comparable with conventional 2D echocardiography in the majority of patients. It can provide new and useful anatomic insight, particularly in patients with mitral valve disease and congenital heart disease. Suboptimal image quality remains a problem for real-time 3D echocardiography in some patients.

Estimation of the End of Ejection in Aortic Stenosis

Background— All indices of aortic stenosis (AS) rely on measurements of mean transvalvular pressure gradient ( ΔP ) and flow rate. Because the gradient is reversed during late ejection, the late systolic left ventricular (LV)–aortic pressure crossover may be an erroneous landmark of end-ejection. The aortic incisura should be a better reference to calculate indices of AS invasively.

Methods and Results— The accuracy of the pressure crossover and the incisura to define end-ejection was assessed in a chronic AS experimental model (9 dogs) with the use of an implantable flowmeter and Doppler echocardiography as reference. In 288 hemodynamic recordings analyzed (aortic valve area [AVA]: 0.74±0.46 cm 2 ), ejection ended 37±29 ms after the pressure crossover but almost simultaneously with the incisura (2±17 ms). Pressure crossover error accounted for significant errors in the measurement of ΔP (95% limits of agreement, +0 to +7 mm Hg) and AVA (−0.1 to +0.2 cm 2 ). These errors were reduced to less than half with the use of the incisura to define end-ejection. Additionally, the agreement with Doppler-derived AS indices was best with use of the incisura. Pressure crossover error was maximal in situations of higher output, moderate orifice narrowing, higher arterial compliance, and lower vascular resistance. In 32 consecutive patients undergoing cardiac catheterization for AS, the pressure crossover induced a clinically important overestimation of the ΔP from +22 to +50%. Errors in AVA estimation were considerably smaller (−2% to +6%) because of simultaneous and offsetting errors in the measurements of ΔP and flow.

Conclusions— The aortic incisura and not the second pressure crossover should be used to obtain invasive indices of AS.

Late incidence and predictors of persistent or recurrent heart failure in patients with aortic prosthetic valves

BACKGROUND

We examined factors associated with persistent or recurrent congestive heart failure after aortic valve replacement.

METHODS

Patients who underwent aortic valve replacement with contemporary prostheses (n = 1563) were followed up with annual clinical assessment and echocardiography. The effect of demographic, comorbid, and valve-related variables on the composite outcome of New York Heart Association class III or IV symptoms or congestive heart failure death after surgery was evaluated with stratified log-rank tests, Cox proportional hazard models, and logistic regression. Factors associated with all-cause death were also examined. Prediction models were bootstrapped 1000 times.

RESULTS

Total follow-up was 6768 patient-years (mean, 4.3 +/- 3.3 years; range, 60 days to 17.1 years). Freedom from congestive heart failure or congestive heart failure death was 98.6% +/- 0.3%, 88.6% +/- 1.0%, 73.9% +/- 2.3%, and 45.2% +/- 8.5% at 1, 5, 10, and 15 years, respectively. Age, preoperative New York Heart Association class, left ventricular grade, atrial fibrillation, coronary artery disease, smoking, and redo status predicted congestive heart failure after surgery (all P <.05). Larger prosthesis size and effective orifice area, both absolute and indexed for body surface area, were independently associated with freedom from congestive heart failure. Increased transprosthesis gradients were predicted by prosthesis-patient mismatch and were associated with congestive heart failure after surgery. Mismatch defined as an effective orifice area/body surface area of 0.80 cm(2)/m(2) or less was a significant predictor of congestive heart failure events after surgery, but mismatch defined as an effective orifice area/body surface area of 0.85 cm(2)/m(2) or less was not. Small prosthesis size and mismatch were not significantly associated with all-cause mortality.

CONCLUSIONS

These analyses identify independent predictors of congestive heart failure symptoms and congestive heart failure death late after aortic valve replacement and indicate that prosthesis size has a significant effect on this cardiac end point, but not on overall survival after aortic valve replacement.

Impending paradoxical embolus: a case report and review of the literature

A case of a 43-year-old man with impending paradoxical embolism (IPE) is described. The patient initially presented with pulmonary embolism and was diagnosed with an IPE on transthoracic and transesophageal echocardiography. He was subsequently treated with heparin and thrombolysis. A comprehensive review of the English literature over the past 20 years identified 60 previously reported cases of IPE. This report discusses the main clinical features, the diagnostic role of echocardiography and the outcome of medical and surgical treatment strategies in patients with IPE. Based on the literature to date, we recommend that patients with impending paradoxical embolism be treated with initial systemic heparinization followed by emergent surgical embolectomy if the surgical risks are acceptable.

Temporal variations in effective orifice area during ejection in patients with valvular aortic stenosis

Effective orifice area (EOA) is the standard index for assessing aortic stenosis (AS) severity. However, EOA varies during ejection and a single measurement at 1 ejection time point may not fully describe the hemodynamic severity of a stenotic aortic valve. We investigated whether the dynamic change in EOA during ejection differs between patients with severe AS (EOA </= 1.0 cm(2)) (n = 15) and age-/sex-matched control patients (n = 15), and whether the ejection pattern varies with AS severity (n = 45). In patients with severe AS, maximum left ventricular outflow tract velocity (V(LVOT)) and transvalvular velocity (V(AS)) occurred later in the ejection period (EP) when compared with control patients (V(LVOT) 47 +/- 8 vs 29 +/- 8%, P =.0001; V(AS) 36 +/- 7 vs 27 +/- 8%, P =.003). Maximum V(LVOT) occurred later than maximum V(AS) in patients with severe AS (47 +/- 8 vs 36 +/- 7%, P =.0005), but simultaneously in control patients (29 +/- 8 vs 27 +/- 8%, P = NS). Patients with severe AS had a slower EOA opening rate than control patients (4 +/- 1 vs 41 +/- 38 cm(2)/s, P =.002) and reached 80% and 100% of maximum EOA later in the EP (43 +/- 26 vs 15 +/- 6%, P =.001; 70 +/- 20 vs 48 +/- 30%, P =.03). EOA tended to increase between 10% and 90% of the EP in patients with severe AS, but had a plateau in control patients (slope 0.38 +/- 0.26 vs 0.02 +/- 0.25% change in EOA per 1% change of EP, P =.0006). In patients with severe AS, EOA was >/=80% of maximum EOA for a shorter duration during ejection compared with control patients (49 +/- 25 vs 64 +/- 14%, P =.05). EOA opening rate, time to maximum V(LVOT), time to maximum V(AS), and time to 80% of maximum EOA correlated with mean pressure gradient (r = -0.80, 0.63, 0.42, and 0.54, respectively, n = 45). Indices of ejection dynamics and valve kinetics differ in patients with AS and may provide further insight into the hemodynamic or physiologic severity of a stenotic aortic valve.

Acute aortic intimal tear without a mobile flap mimicking an intramural hematoma

Several variants of aortic pathology must be considered in the differential diagnosis of the patient presenting with an acute aortic syndrome. In addition to aortic dissection, such entities include intramural hematoma, penetrating aortic ulcer, and localized intimal tear without dissection. These lesions, which lack a mobile intimal flap, may be difficult to correctly identify by transesophageal echocardiography or other imaging modalities. We present a case of an acute aortic syndrome with unusual features on transesophageal echocardiography.

Effect of cardiac resynchronization on myocardial efficiency and regional oxidative metabolism

BACKGROUND

Recent studies have demonstrated increased left ventricular contractility with cardiac resynchronization therapy (CRT) using atriobiventricular stimulation. This study evaluated the effect of CRT on myocardial oxidative metabolism and efficiency.

METHODS AND RESULTS

Eight patients with New York Heart Association functional class III-IV congestive heart failure were studied during atrial pacing (control) and atriobiventricular stimulation at the same rate. The monoexponential clearance rate of [11C]acetate (k(mono)) was measured with positron emission tomography to assess myocardial oxidative metabolism in the left and right ventricles (LV and RV, respectively). Myocardial efficiency was measured using the work metabolic index (WMI). Stroke volume index improved by 10% (P=0.011) with CRT, although both global LV and RV k(mono) were unchanged compared with control. Septal k(mono) increased by 15% (P=0.04), and the septal/lateral wall k(mono) ratio increased by 22% (P=0.01). WMI increased by 13% (P=0.024) with CRT.

CONCLUSIONS

CRT improves LV function without increasing global LV oxidative metabolism, resulting in improved myocardial efficiency. Oxidative metabolism of the interventricular septum increases relative to the lateral wall, which suggests successful resynchronization.

Hemodynamic stability of valve area, valve resistance, and stroke work loss in aortic stenosis: a comparative analysis

BACKGROUND

Although aortic valve area (AVA) has provided the standard index for assessing aortic stenosis severity, valve resistance and percent left ventricular stroke work (%LVSW) loss have been proposed as alternative flow independent indices of stenosis severity that may provide a more stable measure under diverse hemodynamic conditions. In 30 patients with moderate or severe aortic stenosis (AVA < or = 1.2 cm(2)), Doppler echocardiography indices of AVA, valve resistance, and %LVSW loss were measured at multiple transvalvular flow rates during dobutamine infusions (0-10 microg/kg/min) to compare their hemodynamic stability.

RESULTS

From baseline to maximum dobutamine dose in the 30 patients, transvalvular flow rate increased 43% and resulted in a 42% increase in mean transvalvular pressure gradient, a 15% increase in Doppler AVA, and a 26% increase in %LVSW loss. Group mean valve resistance did not change for the total cohort. For individual patients, AVA and %LVSW loss demonstrated a linear relationship with transvalvular flow (median r = 0.74 and 0.84, respectively). In contrast, both flow-mediated increases and decreases in valve resistance were observed in individual patients, resulting in the apparent stability of the group mean valve resistance in the total cohort. For individual patients, Doppler AVA and valve resistance demonstrated comparable stability in response to changes in hemodynamic conditions and were significantly more stable than mean transvalvular pressure gradient and %LVSW loss.

CONCLUSION

Doppler AVA and valve resistance provide stenotic indices of equivalent hemodynamic stability. However, transvalvular flow has a predictable directional effect on AVA and an unpredictable directional effect on valve resistance, potentially limiting valve resistance as a measure of hemodynamic severity.

In-vivo analysis of the instantaneous transvalvular pressure difference-flow relationship in aortic valve stenosis: implications of unsteady fluid-dynamics for the clinical assessment of disease severity

BACKGROUND AND AIM OF THE STUDY

Because the hemodynamic basis of aortic valve area (AVA) has never been validated in vivo, several alternative indices have been proposed to quantify the severity of aortic stenosis (AS). This study was designed to assess the fluid-dynamics of aortic valve stenosis in order to clarify which index best accounts for disease severity. The diagnostic implications of reversed deltaP during ejection were also investigated.

METHODS

Chronic valvular AS characterized by stiff leaflets without commissural fusion was created surgically in eight adult mongrel dogs; three additional animals were used as controls. At two-week intervals (three studies per dog), simultaneous micromanometer pressure and transit-time Q measurements were collected under different hemodynamic conditions. Instantaneous deltaP and Q signals were processed digitally and fitted to a modified form of the unsteady Bernoulli equation in which AS is characterized by effective valve area.

RESULTS

An unsteady Bernoulli equation accurately predicted measured instantaneous AP values (R = 0.97+/-0.06), and a quadratic correlation was observed between instantaneously fitted and Gorlin-derived AVA. Additionally, deltaP < 0 mmHg during late ejection was observed in the majority of AS datasets, with a normalized time to deltaP reversal of 93+/-13% for AS animals versus 69+/-36% for controls (p <0.0005). Time to deltaP reversal inversely correlated with the Strouhal number (R = -0.77), and was responsible for an overestimation of mean systolic transvalvular deltaP and Q that resulted in a significant bias in the Gorlin method. Error was highest in moderate stenosis with low transvalvular output.

CONCLUSION

Unsteady fluid-dynamics supports AVA over other measures of AS such as aortic valve resistance. However importantly, late-ejection reversal of deltaP precludes estimating the systolic ejection period from pressure tracings, and accounts for an additional source of error when AS is quantified invasively.

Direct drainage of the right pulmonary veins into the coronary sinus with intact interatrial septum: a case report

Partial anomalous pulmonary venous connection to the coronary sinus is rare. This anomaly is even more rare in the absence of interatrial communication. Usually, the anomalous right pulmonary veins drain to the right atrium or venae cavae, while the anomalous left veins connect to the coronary sinus or left innominate vein. The present report is the first in the English literature to document a situs solitus case in which all three right pulmonary veins drained directly into the coronary sinus without an atrial septal defect. Closure of the coronary sinus orifice and unroofing of the coronary sinus into the left atrium is a safe and effective way of treating this anomaly.

Isolated pulmonic valve endocarditis in healthy hearts: a case report and review of the literature

The case of a 53-year-old man with isolated pulmonic valve endocarditis in a structurally normal heart is presented. The patient had a history of chronic obstructive pulmonary disease and was admitted to hospital with an apparent exacerbation with pneumonia. Blood cultures grew Staphylococcus aureus, and an echocardiogram identified a large vegetation on the pulmonic valve in a structurally normal heart. He was unsuccessfully treated with antibiotics and eventually required pulmonic valve replacement. The literature from 1960 to 1999 identified only 36 reported cases of pulmonic valve endocarditis in structurally normal hearts. The present report underscores the importance of suspecting pulmonic valve endocarditis in patients with multiple pulmonary lesions, and discusses the predisposing factors, clinical features, diagnostic role of echocardiography and the potential benefits of early surgical treatment.