Transseptal pressure gradient and diastolic ventricular septal motion in patients with mitral stenosis

Previous studies from our laboratory have shown that the position of the ventricular septum relative to the two ventricles at end-diastole is determined by the instantaneous transseptal pressure gradient (TSG) defined as left ventricular minus simultaneous right ventricular pressure. Since patients with mitral stenosis often have exaggerated leftward (paradoxic) motion of the ventricular septum during early diastole, we studied seven patients with mitral stenosis undergoing cardiac catheterization to determine if position (and therefore motion) of the ventricular septum was determined by TSG throughout diastole. M Mode echocardiograms derived from a two-dimensional parasternal short-axis view were recorded with simultaneous micromanometer measurements of left ventricular and right ventricular pressures. Six of seven patients demonstrated abnormal early diastolic leftward motion of the ventricular septum in at least one cardiac cycle. TSG measured at intervals throughout diastole ranged from -2.5 to +20 mm Hg, with abnormal TSG observed in most of the 40 cardiac cycles selected for analysis. The intracardiac position of the ventricular septum, defined as the distance from the right ventricular epicardium (RVEpi) to the left surface of the ventricular septum normalized for total cardiac dimension (RVEpi-VS), was plotted against left ventricular pressure, right ventricular pressure, and TSG. Linear regression of pooled data from all patients (164 observations) demonstrated a highly significant correlation between the instantaneous TSG and the relative intracardiac position of the ventricular septum (RVEpi-VS = 1.52 TSG + 42.7; r = .79, p less than .0001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Quantitative two-dimensional echocardiography in massive pulmonary embolism: emphasis on ventricular interdependence and leftward septal displacement

In 14 patients requiring aggressive therapy for circulatory failure resulting from massive pulmonary embolism, hemodynamic and two-dimensional echocardiographic data were obtained at bedside (acute phase) and again after circulatory improvement (intermediate phase) and during recovery. The acute stage was characterized by a low cardiac output state despite inotropic support (cardiac index 1.9 +/- 0.6 liters/min per m2) associated with increased right atrial pressure (12.4 +/- 4.2 mm Hg), increased right ventricular end-systolic and end-diastolic area (12.4 +/- 3.4 and 15.4 +/- 4.1 cm2/m2, respectively) and reduced right ventricular fractional area contraction (20.1 +/- 8.6%). Two-dimensional echocardiography also revealed interventricular septal flattening at both end-systole and end-diastole and markedly decreased left ventricular end-diastolic dimensions. Left ventricular fractional area contraction remained normal. Hemodynamic improvement occurred during the intermediate phase as shown by restoration of cardiac index (3.3 +/- 0.6 liters/min per m2), decrease in right atrial pressure (8.3 +/- 4.8 mm Hg), reduction in right ventricular end-systolic area (9.0 +/- 3.6 cm2/m2 at the intermediate stage and 6.1 +/- 1.8 cm2/m2 at recovery) and end-diastolic area (10.5 +/- 3.6 cm2/m2 at the intermediate stage and 8.9 +/- 2.9 cm2/m2 at recovery) and improvement in right ventricular fractional area contraction (31.5 +/- 16.4%). The interventricular septum progressively returned to a more normal configuration at both end-systole and end-diastole, and left ventricular diastolic dimension steadily increased. It is concluded that circulatory failure secondary to massive pulmonary embolism was mediated through a profound decrease in left ventricular preload, resulting from both pulmonary outflow obstruction and reduced left ventricular diastolic compliance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Valsalva's manoeuvre and hyoscinbutylbromide on the pressure gradient across the wall of oesophageal varices.

To assess whether Valsalva's manoeuvre might cause variceal bleeding, 22 patients with oesophageal varices were studied. In 12 patients who received no previous treatment to their varices the median pressure gradient across the varix wall at rest was 19 (6-36) mmHg, and in 10 patients whose varices were thrombosed at their distal end the median pressure gradient in the proximal patent varix was 8 (1-6) mmHg. In untreated patients groups, the pressure gradient rose by 6-12 mmHg during Valsalva's manoeuvre in four patients, fell by 4-11 mmHg in five patients and was virtually unchanged in the remainder. These changes seem unlikely to cause variceal bleeding. Patients who repeated Valsalva's manoeuvre showed similar changes on each occasion. Six patients in the untreated group also received hyoscinbutylbromide 20 mg iv. No change was seen in the pressure gradient in five patients, suggesting that it is of little value in preventing variceal bleeding.     

Continuous-wave Doppler in children with ventricular septal defect: noninvasive estimation of interventricular pressure gradient

Continuous-wave Doppler was used to estimate the pressure gradient between the right and left ventricles in 28 children with ventricular septal defect (VSD). Doppler measurement of maximal velocity was performed during cardiac catheterization and the Doppler-predicted gradient was compared with the peak-to-peak gradient measured simultaneously by catheter. Doppler gradients ranged from 10 to 71 mm Hg and correlated well with measured gradient (r = 0.97, p greater than or equal to 0.001). Fourteen patients had isolated VSD, and in these patients Doppler measurements of gradient allowed accurate estimation of right ventricular pressure (r = 0.93). There was an inverse correlation between the ratio of pulmonary to systemic resistance and maximal velocity (r = -0.77). Thus, continuous-wave Doppler is an accurate means of measuring instantaneous VSD pressure gradient in children with congenital heart disease and can be used to estimate the right ventricular and pulmonary artery pressure in children with isolated VSD. This noninvasive method can be used to distinguish restrictive from nonrestrictive VSD.     

Transseptal approach in children after patch occlusion of atrial septal defect: first experience with the cutting balloon.

Two children required a transseptal approach to the left heart for endovascular stent redilation late after pericardial patch closure of atrial septal defects performed at the time of their initial surgical intervention. Following perforation of thickened interatrial patches in both patients, cutting balloons were used to create adequate interatrial communications. Cathet. Cardiovasc. Intervent. 48:378-381, 1999.     

The bradycardic response to the Valsalva manoeuvre in normal man

To elucidate whether the Valsalva manoeuvre (VM) can produce a bradycardia instead of well-known tachycardia, a systemic study of the influence of various degrees of strain pressure and lung volumes was undertaken. Six basic patterns beat-to-beat heart rate response (HRR) were seen during the inspiratory graded VM straining with a duration of 25 sec in 75 healthy male subjects (undergraduates) aged 19-28 years. Two patterns were bradycardic, three patterns tachycardic, and one intermediate. The conditions favouring within-strain bradycardia included: completely expanded lungs, low expiratory strain pressure, and a vagotonic state of autonomic reactivity. In order to explore the mechanisms for the bradycardia-type response, in an additional subset of six subjects the instantaneous changes in the arterial mean pressure and vascular resistance were studied. Despite of conspicuous bradycardia the well-known classical four-phase course in blood pressure appeared (Hamilton et al., 1936. J. Am. Med. Assoc. 107, 853-856). We suggest that the nature of HRR to inspiratory VM is determined by the balance between two reflex influences -a vagal reflex from slowly adapting pulmonary stretch receptors and a sympathetic reflex from arterial baroreceptors. It was concluded that the bradycardic HRR to inspiratory VM is a normal event in men with parasympathetic reactivity, particularly when strain pressure is low.     

Continuous non-invasive blood pressure monitoring: reliability of Finapres device during the Valsalva manoeuvre

Because of the inherent risks of intra-arterial blood pressure monitoring a new non-invasive device, Finapres, which measures blood pressure continuously in the finger, was evaluated in 14 hypertensive and one normotensive subject. Brachial intra-arterial and finger pressures were compared during a control period and a subsequent Valsalva manoeuvre. Visually, blood pressures measured by Finapres faithfully reproduced the intra-arterial recordings in all subjects. From each pressure signal beat to beat systolic, diastolic, and mean blood pressure values and their differences were obtained and the time course of the response and its characteristic features were analysed. During the control period the Finapres measurements were lower than intra-arterial systolic, mean, and diastolic pressures (mean(SD) 1(9.6), 9(6.8), and 4(6.1) mmHg respectively). During the response to the Valsalva manoeuvre the brachial-finger pressure differences showed limited deviation from those during the control period; median differences were at most 6 mmHg occurring late during the intrathoracic strain period and 7 mmHg during the post-release blood pressure overshoot. In general, the Finapres device reproduced intra-arterial patterns faithfully. This device appears to offer a reliable alternative to intra-arterial blood pressure monitoring.     

Determinants of aortic pressure variation during positive-pressure ventilation in man.

STUDY OBJECTIVES: To define the relation between systolic arterial pressure (SAP) changes during ventilation and left ventricular (LV) performance in humans. DESIGN: Prospective repeat-measures series. SETTING: University of Pittsburgh Medical Center Operating Room. PATIENTS: Fifteen anesthetized cardiac surgery patients before and after cardiopulmonary bypass when the mediastinum was either closed or open. Interventions: Positive-pressure ventilation. MEASUREMENTS AND RESULTS: SAP and LV midaxis cross-sectional areas were measured during apnea and then were measured for three consecutive breaths. SAP increased during inspiration, this being the greatest during closed chest conditions (p < 0.05). Changes in SAP could not be correlated with changes in either LV end-diastolic areas (EDAs), end-systolic areas, or stroke areas (SAs). If SAP decreased relative to apnea, the decrease occurred during expiration and was often associated with increasing LV EDAs and SAs. SAP often decreased after a positive-pressure breath, but the decrease was unrelated to SA deficits during the breath. Increases in SAP were in phase with increases in airway pressure, whereas decreases in SAP, if present, followed inspiration. No consistent relation between SAP variation and LV area could be identified. CONCLUSIONS: In this patient group, changes in SAP reflect changes in airway pressure and (by inference) intrathoracic pressure (as in a Valsalva maneuver) better than they reflect concomitant changes in LV hemodynamics.     

Decay rate of inspiratory muscle pressure during expiration in man.

Decay rate of inspiratory muscle pressure (PmusI) was studied in 4 subjects during post-inspiratory period of zero flow (TEz) occurring under discontinuous inspiratory elastic load (DIL). End-inspiratory pressure (PmuseI) was increased by dead spaces or exercises. Decay rate was related to PmuseI by a power function with exponent greater than 1. It was not directly affected by concomitant changes of PCO2. It did not increase when an expiratory resistive load was added, i.e. when braking action of inspiratory muscles was no longer required. Time course of PmusI during TEz was more straight than exponential. Relative decay rate increased with PmuseI and with decrease of inspiratory or expiratory time. Experiments with resistive loads suggest that relative rate is mainly related to timing factors. During voluntary inspiratory efforts with closed airways, relative decay rate was not related to PmuseI, while decay rate increased linearly with PmuseI.     

Doppler echocardiographic assessment of the pressure gradient during bicycle ergometry in hypertrophic cardiomyopathy.

To assess the behavior of the subvalvular pressure gradient under physical exercise, 13 patients with obstructive hypertrophic cardiomyopathy were examined during upright bicycle ergometry by means of Doppler echocardiography. Additionally, right-sided cardiac catheterization was performed within 7 days. In 10 patients adequate Doppler tracings could be obtained during exercise. The Doppler-derived systolic pressure gradient increased from 75 +/- 24 to 140 +/- 42 mm Hg (p less than 0.0005). This was associated with an increase in the duration of the systolic mitral-septal contact from 59 +/- 21 to 136 +/- 28 ms (p less than 0.0005). Correlation between the pressure gradient and the duration of mitral-septal contact at rest and during exercise was good (r = 0.86), whereas correlation between the resting and exercise pressure gradient (r = 0.34) did not reach statistical significance. The increase in stroke volume during exercise, from 90 +/- 18 to 95 +/- 24 ml, was significant (p less than 0.05) but minimal. Therefore, only a moderate increase in systolic flow, from 205 +/- 54 to 268 +/- 78 ml/s (p less than 0.0005), was observed. Outflow tract resistance, defined as the ratio of the pressure gradient to systolic flow, increased from 0.38 +/- 0.11 to 0.57 +/- 0.24 mm Hg.s/ml (p less than 0.01). Thus, in a selected group of patients with hypertrophic cardiomyopathy a substantial increase in the maximal pressure gradient during upright bicycle ergometry was demonstrated in most patients. Exercise Doppler echocardiography may be valuable to assess the hemodynamic significance of obstruction in individual patients in a physiologic setting and has a potential to monitor the effect of therapeutic interventions.     

Airway anesthesia during positive and negative inspiratory pressure breathing in man.

We have measured the effects of airway anesthesia (aerosolized 5% lidocaine) on the respiratory pattern during positive or negative inspiratory pressure in 8 resting subjects. The subjects breathed through a 600 ml dead space (peak inspiratory airway pressure, Paw = -2 cmH2O) without or with negative (approx. -5 or -10 cmH2O) or positive (approx. +5 or +10 cmH2O) inspiratory pressure, provided by a laminar flow resistance or a positive pressure source, respectively. Control measurements were performed before and after measurements with airway anesthesia. Measurements included tidal volume, respiratory frequency, ventilation, inspiratory and expiratory duration, occlusion pressure (P0.1) and end-tidal PCO2. None of the parameters measured was significantly altered by airway anesthesia, which was effective in suppressing the cough reflex. We conclude that information from lung afferents that are suppressed with the elimination of the cough reflex is not important for the breathing pattern during resting ventilation with elevated tidal volume (dead space load) and with positive or negative inspiratory pressure.     

Obstructive sleep apnea syndrome with reversible interventricular septal displacement during sleep: a case report

A case of the obstructive sleep apnea syndrome revealed reversible leftward displacement of the interventricular septum by echocardiography during sleep. A 46-year-old housewife with congenital micrognathia was admitted to our hospital complaining of severe dyspnea and general edema. On admission, she had severe hypoxemia (PaO2 = 35.2 mmHg), pulmonary hypertension (mean pulmonary artery pressure = 70 mmHg) and right heart failure. Her echocardiograms revealed enlargement of the right ventricle with a flattened left ventricle. A sleep study performed after partial resolution of her right heart failure disclosed that severe hypoxemia and pulmonary hypertension (mean pulmonary artery pressure = 70 mmHg) occurred after relatively long periods of apnea. With vigorous inspiratory efforts during sleep apnea, transient enlargement of the right ventricle and leftward displacement of the septum causing the flattened left ventricle were observed echocardiographically. A concomitant decrease in left ventricular inflow velocities was also observed by the pulsed Doppler method. However, these findings immediately returned to normal with the resumption of ventilation. We concluded that these repetitive apneic events due to obstruction of the airway during sleep might accelerate complete eventual pulmonary hypertension and right heart failure.     

Magnetic resonance imaging differentiated partial from complete absence of the left pericardium in a case of leftward displacement of the heart.

A 44-year-old man was referred to hospital for the evaluation of atypical chest pain. His chest X-ray showed leftward displacement of the heart. During echocardiography, the apical window displaced laterally in the usual left lateral position and characteristic motions of the interventricular septum and left ventricular posterior wall were recognized with postural alterations. We presumed a complete absence of the left pericardium. Magnetic resonance imaging (MRI), however, demonstrated a partial left-sided pericardium. The diagnosis was corrected to partial absence of the left pericardium and we have carefully followed up this case without surgical prophylactic intervention. It is very important to differentiate partial from complete absence of the pericardium, because only in patients with partial absence of the pericardium is there a risk of fatal myocardial strangulation. The features of the chest X-ray and echocardiography of this case, which strongly suggested complete absence of the left pericardium, are possibly not always reliable signs. In cases with these abnormal imaging features, MRI may provide additional useful information, as in this case.     

Load compensation during positive pressure breathing in anesthetized man

To investigate the mechanisms by which human subjects prevent or compensate for the change in respiratory muscle length imposed by applying continuous positive pressure to the airways, six men were studied under general anesthesia with methoxyflurane at the end of a minor surgical procedure (rhinoplasty). Ventilatory and occlusion pressure response to carbon dioxide was measured by a rebreathing technique with no bias pressure, or with 16 cm H2O positive pressure produced by adding weights to a spirometer bell. Static pressure-volume curves of the respiratory system were obtained while the subjects were paralyzed with succinyl choline. In contrast to awake subjects described in other studies, the anesthetized patients did not activate expiratory muscles to combat the rise in end-expiratory level caused by pressure, and showed little evidence of enhanced activation of inspiratory muscles that in the conscious state compensates for the disadvantage of their shorter length. A change in the shape of the occlusion pressure wave, however, suggested that positive pressure had some effect on the neural discharge to inspiratory muscles. The mechanisms by which the respiratory system defends itself against a pressure load that tends to change end-expiratory level are sensitive to anesthesia and may require consciousness.     

Muscle activity during chest wall restriction and positive pressure breathing in man.

The effects of sustained constriction of the rib cage (RCC), constriction of the abdomen (AC) and of breathing against a positive pressure of 10 cms of water (PPB) were studied in four normal subjects with moderate constant hypercapnia. Intercostal electrical activity (Eic) was measured by implanted wire electrodes and diaphragmatic electrical activity (Edia) by oesophageal electrodes. There was no fixed relation between Edia and VT. VT was unaltered during AC and RCC: Edia was unaltered during AC but increased during RCC. The response to PPB without constriction varied: three subjects increased end-expiratory VL with increase in Edia and inspiratory Eic. One subject initially, and one subject after training, maintained end-expiratory VL constant with no change in Edia and an increase in expiratory Eic. When PPB was applied during AC and RCC there was an increase in Edia proportional to end-expiratory lung volume. The overall response to distortion was determined by voluntary choice, but muscle electrical activity reflected chest wall configuration: when the diaphragm was shorter and at a mechanical disadvantage its electrical activity increased. This was compatible with a reflex with afferent information from diaphragm tendon organ and muscle spindle receptors.