Rise In Right Ventricular Pressure Research Articles

IL-33/ST2 receptor-dependent signaling in the development of pulmonary hypertension in Sugen/hypoxia mice.

Pulmonary arterial hypertension (PAH) is associated with significant morbidity and mortality. PAH is characterized by pulmonary artery remodeling, elevated right ventricular pressure (RVP) and, ultimately, cardiac failure. Pulmonary endothelial cells can sense danger or damage caused by mechanical injury or pathogens through alarmin cytokines. These cytokines can signal proliferation to restore barrier integrity or aberrant hyperproliferation and remodeling. We hypothesized that IL‐33 signals pulmonary artery endothelial cells to proliferate under hypertensive conditions during the remodeling response and rise in RVP. To test this hypothesis, pulmonary hypertension (PH) was induced in C57Bl/6J, IL‐33 receptor gene deleted (ST2−/−) and MYD88 gene deleted (MYD88−/−) mice by exposure to 10% O2 and SU5416 injections (SUHX). RVP, arterial wall thickness, endothelial cell proliferation and IL‐33 levels and signaling were evaluated. In response to SUHX. RVP increased in C57Bl/6J mice in response to SUHX (49% male and 70% female; p < 0.0001) and this SUHX response was attenuated in ST2−/− mice (29% male p = 0.003; 30% female p = 0.001) and absent in MYD88−/− mice. Wall thickness was increased in SUHX C57Bl/6J mice (p = 0.005), but not in ST2−/− or MYD88−/− mice. Proliferating cells were detected in C57Bl/6J mice by flow cytometry (CD31+/BrDU+; p = 0.02) and immunofluorescence methods (Ki‐67+). IL‐33 was increased by SUHX (p = 0.03) but a genotype effect was not observed (p = 0.76). We observed that in hPAECs, IL‐33 expression is regulated by both IL‐33 and DLL4. These data suggest IL‐33/ST2 signaling is essential for the endothelial cell proliferative response in PH.

336 Right ventricular mechanics in patients affected by pulmonary valve stenosis, before and after percutaneous pulmonary angioplasty

Abstract Aims Pulmonary valve stenosis accounts for 6–9% of all congenital heart diseases. The main effect of this obstructive lesion is a rise in right ventricular pressure; this overload leads to multiple changes in shape, dimensions, and volume of the ventricle. The diagnosis is based on transthoracic echocardiography and invasive heart catheterization. Usually the stenosis is classified into mild, moderate, and severe based on pressure gradient between right ventricle and pulmonary artery and on the ratio between right ventricle and left ventricle systolic pressure. Percutaneous balloon valvuloplasty is the treatment of choice in severe pulmonary valve stenosis in patients of all ages; alternatively surgical valvotomy is an option in selected cases. The aim of this study is to evaluate the mechanical changes of the right ventricle in patients undergoing balloon pulmonary valvuloplasty using transthoracic and speckle-tracking echocardiography (STE). Furthermore, we sought to investigate the correlation between haemodynamic and echocardiographic parameters to better evaluate the degree of pulmonary valve stenosis before and after treatment. Methods and results Forty-three pediatric patients (19 males), mean age 3.2 ± 4.9 years with severe pulmonary valve stenosis and indication for percutaneous balloon valvuloplasty were recruited at the University Hospital of Padua. All patients underwent standard transthoracic echocardiography (TTE), STE with analysis of right ventricle global longitudinal strain (RVGLS) one day before and one day after the procedure. For each patient were collected invasive parameters during the interventional procedure before and after balloon valvuloplasty. After the procedure, there was an immediate statistically significant reduction of both peak-to-peak transpulmonary gradient (Dp post) and ratio between the systolic pressure of right and left ventricle (RV/LV ratio) with a drop of 29.3 ± 14.67 mmHg and 0.43 ± 0.03, respectively. Post-procedural echocardiography showed peak and mean transvalvar pressure gradient drop (50 ± 32.23 and 31 ± 17.97, respectively). The degree of pulmonary valve regurgitation was mild in 8% of patients before the procedure, following the intervention it reached 29% with a statistically significant increase (P = 0.007). However, the incidence of pulmonary valve moderate and severe regurgitation remained stable after the procedure. The analysis of right ventricular function and mechanics showed a significant improvement of Fractional Area Change (FAC) immediately after the procedure (40.11% vs. 44.42%, P = 0,01). On the other hand, right ventricular longitudinal systolic function parameters, TAPSE (P = 0.60) and longitudinal strain (P = 0.31), did not improve significantly after intervention. Finally, pre-procedural invasive RV/LV ratio showed good correlation to echocardiographic transvalvular peak and mean pressure gradient (R = 0.375, P = 0.019 and R = 0.40, P = 0.012, respectively), as well as with FAC (R = 0.31, P = 0.05), TAPSE (R = 0.62, P &amp;lt; 0.001), and RVGLS (R = 0.46, P = 0.01). Conclusions Percutaneous balloon pulmonary valvuloplasty represents an efficient and safe procedure to relieve severe pulmonary valve stenosis. Interestingly, the analysis of right ventricular mechanics on echocardiography demonstrated an immediate global systolic function improvement following afterload reduction. Conversely, longitudinal systolic function did not show improvement immediately after intervention, possibly due to the necessity of longer time to recover. Finally, invasive preprocedural RV/LV ratio demonstrated better correlation with echocardiographic evaluation of stenosis degree and right ventricular function compared to invasive peak-to-peak pressure gradient. Therefore, RV/LV ratio should be preferred for the assessment of pulmonary valve stenosis.

Mechanism of the right ventricular reverse remodeling after balloon pulmonary valvuloplasty in patients with congenital pulmonary stenosis: A three-dimensional echocardiographic study.

Background and Objectives:The main effect of pulmonary stenosis is a rise in right ventricular pressure. This pressure overload leads to multiple changes in the shape, dimensions, and volumes of the right ventricle (RV) that are reversed after the relieve of the valve obstruction. We thought to study the changes in the RV in patients undergoing balloon pulmonary valvuloplasty (BPV) using three-dimensional (3D) echocardiography.Subjects and Methods:The study included 50 patients with isolated valvular pulmonary stenosis who underwent BPV at our hospital from December 2016 to August 2017; echocardiography was recorded preprocedural and 3 months after the procedural.Results:The median age of the study group at the time of the procedure was 2.7 years. The indexed RV wall thickness, basal, and mid-right ventricular dimensions decreased significantly after the procedure (P < 0.005), and the longitudinal dimension increased significantly after the procedure (P < 0.005). The end-systolic and the end-diastolic volumes (EDVs) by 3D echocardiography increased insignificantly (P > 0.05), and the right ventricular function increased significantly (P < 0.05), indicating that the changes in the EDVs were more than the changes in the end-systolic volumes.Conclusions:There are several factors that interplay together and result in reverse remodeling of the RV after BPV including regression in the RV hypertrophy; changes in the interventricular septal morphology, bowing, and mobility; and changes in the ventricular geometry and dimensions, rather than changes in the ventricular volumes.

Trimedazidine alleviates pulmonary artery banding-induced acute right heart dysfunction and activates PRAS40 in rats.

The molecular mechanism underlying acute right heart failure (RHF) is poorly understood. We used pulmonary artery banding (PAB) to induce acute RHF characterized by a rapid rise of right ventricular pressure, and then a decrease in right ventricular pressure along with a decrease in blood pressure right after banding. We found higher brain natriuretic peptide (BNP) and beta-myosin heavy chain (βMHC) levels and lower alpha-myosin heavy chain (αMHC) levels in RHF rats than sham-operated rats. Hemodynamic indexes in rats with acute RHF were slightly improved by trimedazidine TMZ, a key inhibitor of fatty acid (FA) oxidation. TMZ also reversed downregulation of peroxisome proliferator-activated receptor gamma coactivator 1-beta (PGC-1β) and peroxisome proliferator-activated receptor alpha (PPARα) by PAB and up-regulates peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), peroxisome proliferator-activated receptor delta (PPARδ) and pyruvate dehydrogenase kinase isoform 4 (PDK4). In addition, TMZ reversed upregulation of phosphorylated Akt by PAB and increased phosphorylated proline-rich Akt-substrate 40 (PRAS40). Autophagy and apoptosis were not modified by PAB or TMZ. An acute RHF model was established in rats through 70% constriction of the pulmonary artery. TMZ treatment alleviated PAB-induced acute RHF by activating PRAS40 and upregulatingPGC-1α, PGC-1β, PPARα, PPARδ, and PDK4.

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Delayed depolarization of the cog-wheel valve and pulmonary-to-systemic shunting in alligators.

Alligators and other crocodilians have a cog-wheel valve located within the subpulmonary conus, and active closure of this valve during each heart beat can markedly and phasically increase resistance in the pulmonary outflow tract. If this increased resistance causes right ventricular pressure to rise above that in the systemic circuit, right ventricular blood can flow into the left aorta and systemic circulation, an event known as pulmonary-to-systemic shunting. To understand better how this valve is controlled, anaesthetized American alligators (Alligator mississippiensis) were used to examine the relationships between depolarization of the right ventricle, depolarization/contraction of the cog-wheel valve muscle and the resultant right ventricular, pulmonary artery and systemic pressures. Depolarization swept across the right ventricle from the apex towards the base (near where the cog-wheel valve muscle is located) at a velocity of 91+/-23 cm s(-1) (mean +/- S.E.M., N=3). The cog-wheel valve electrocardiogram (ECG) (and thus contraction of the valve) trailed the right ventricular ECG by 248+/-28 ms (N=3), which was equivalent to 6-35 % of a cardiac cycle. This long interval between right ventricular and valve depolarization suggests a nodal delay at the junction between the base of the right ventricle and the cog-wheel valve. The delay before valve closure determined when the abrupt secondary rise in right ventricular pressure occurred during systole and is likely to strongly influence the amount of blood entering the pulmonary artery and thus to directly control the degree of shunting. Left vagal stimulation (10-50 Hz) reduced the conduction delay between the right ventricle and cog-wheel valve by approximately 20 % and reduced the integrated cog-wheel ECG by 10-20 %. Direct application of acetylcholine (1-2 mg) also reduced the integrated cog-wheel ECG by 10-100 %; however, its effect on the conduction delay was highly variable (-40 to +60 %). When the cog-wheel valve muscle was killed by the application of ethanol, the cog-wheel ECG was absent, right ventricular and pulmonary pressures remained low and tracked one another, the secondary rise in right ventricular pressure was abolished and shunting did not occur. This study provides additional, direct evidence that phasic contraction of the cog-wheel valve muscle controls shunting, that nervous and cholinergic stimulation can alter the delay and strength of valve depolarization and that this can affect the propensity to shunt.

Deficiency of urokinase-type plasminogen activator-mediated plasmin generation impairs vascular remodeling during hypoxia-induced pulmonary hypertension in mice.

Chronic hypoxia results in the development of pulmonary hypertension and subsequent right heart failure. A role of the plasminogen system in the pathogenesis of pulmonary hypertension and pulmonary vascular remodeling has been suggested. Mice with targeted deficiency of the gene encoding tissue-type plasminogen activator (t-PA(-/-)), urokinase-type plasminogen activator (u-PA(-/-)), u-PA receptor (u-PAR(-/-)), or plasminogen (plg(-/-)) were subjected to hypoxic conditions. Hypoxia caused a significant 2.5-fold rise in right ventricular pressure in wild-type mice. Deficiency of u-PA or plasminogen prevented this increase in right ventricular pressure, t-PA(-/-) mice showed changes that were fully comparable with wild-type mice, and u-PAR(-/-) mice showed a partial response. Hypoxia induced an increase in smooth muscle cells within pulmonary arterial walls and a vascular rarefaction in the lungs of wild-type but not of u-PA(-/-) or plg(-/-) mice. Elastic lamina fragmentation, observed in hypoxic wild-type but not in u-PA or plasminogen-deficient mice, suggested that proliferation of vascular smooth muscle cells was dependent on u-PA-mediated elastic membrane degradation. Hypoxia-induced right ventricular remodeling in wild-type mice, characterized by cardiomyocyte hypertrophy and increased collagen contents, was not seen in u-PA(-/-) and plg(-/-) mice. Loss of the u-PA or plasminogen gene protects against the development of hypoxia-induced pulmonary hypertension and pulmonary vascular remodeling. These observations point to an essential role of u-PA-mediated plasmin generation in the adaptive response to chronic hypoxia and the occurrence of hypoxic pulmonary vascular disease.

Heart rhythm disturbances during the acute period of massive pulmonary embolism.

We studied the type, incidence, and dynamics of arrhythmia during the acute phase of massive pulmonary embolism complicated or uncomplicated by cardiac insufficiency. Complicated and uncomplicated massive pulmonary embolisms were accompanied by the appearance of individual and allorhythmic ventricular extrasystoles, respectively. The rise of right ventricular pressure to 70 mm Hg was critical for the development of allorhythmia. Allorhythmia started 3-268 sec after attaining critical ventricular pressure. Heart rhythm spontaneously recovered in 100 and 78% animals with uncomplicated and complicated massive pulmonary embolism, respectively. The duration of paroxysmal allorhythmia varied from 15 sec to 15 min. Electrophysiological processes in the myocardium were normalized with progression of uncomplicated massive pulmonary embolism: the incidence of single and, in particular, allorhythmic extrasystoles decreased, and electrocardiographic parameters returned to normal.

Protection by Estradiol 17β Against the Development of Hypoxic Pulmonary Hypertension in Male Rats

We evaluated the effect of estradiol 17β treatment on the development of pulmonary hypertension and vascular remodeling in male rats exposed to chronic hypoxia. Rats were treated with either placebo or estradiol 17β slow release pellets and exposed to either normoxic air or 10% oxygen for 10 days. Hypoxia elevated right ventricular pressure (RVP) from 19.0 ± 1.5 mm Hg in placebo normoxic to 34.4 ± 1.6 mm Hg in hypoxic animals (p < 0.01). Hypoxia also increased the right ventricle to left ventricle + septum weight ratio (RV/LV + S) (from 0.29 ± 0.01 to 0.44 ± 0.01; p < 0.01) and increased medial thickening in distal pulmonary vessels (from 7.4 ± 1.1% to 14.9 ± 1.4%; p < 0.01). Estradiol treatment blunted the rise in RVP (23.3 ± 2.4 mm Hg; p < 0.01), the RV/LV + S ratio (0.28 ± 0.05; p < 0.01), and vascular medial thickening (9.2 ± 0.8%; p < 0.05) in hypoxic animals, but did not significantly affect these parameters in normoxic rats. Estradiol produced a comparable decrease in hematocrit in both normoxic an...

Phasic characteristics of arterial inflow and venous outflow of right ventricular myocardium in dogs.

To clarify the characteristics and causes of phasic blood flow in coronary circulation of the right ventricle we measured blood velocities in peripheral portions of the right coronary artery and vein in dogs under three conditions: control, transient pulmonary stenosis, and isoproterenol administration. An optical fiber sensor of a laser Doppler velocimeter was fixed onto the vessels (150-500 microns OD) with cyanoacrylate. The phasic pattern of distal arterial velocity was compared with the proximal velocity in the right coronary artery measured with an ultrasound pulsed Doppler velocimeter. Systolic-to-total velocity area ratio in the small epicardial artery [0.38 +/- 0.03 (SE)] was found to be smaller than in the large epicardial artery (0.51 +/- 0.02, P less than 0.01), indicating a capacitive filling of the epicardial artery during systole. The velocity waveform in small right coronary veins was predominantly systolic; i.e., it increased with a rise of right ventricular pressure and decreased with right ventricular relaxation. Comparison of the waveforms during isoproterenol infusion and pulmonary stenosis indicates that contraction of the ventricle is more important than right ventricular systolic pressure in retarding arterial inflow and accelerating venous outflow.

Development of a rate adaptive pacemaker based on the maximum rate-of-rise of right ventricular pressure (RV dP/dtmax).

The maximum rate of rise of right ventricular pressure (RV dP/dtmax) may change in response to physiological stress and thereby provide an appropriate parameter upon which to base rate adaptive pacing. Initial feasibility testing was carried out in six patients using externally closed loop rate adaptive pacing with a pressure sensing lead (Model 6220) and an investigational VVI pulse generator (Medtronic, Model 2451). During exercise, maximum positive RV dP/dtmax increased from 223 +/- 55 to 405 +/- 181 mmHg.sec.1 (P less than 0.05). Based on these results, rate adaptive pulse generators using maximum positive RV dP/dt were implanted in 12 patients (Medtronic, Model 2503). Exercise treadmill testing in the VVI mode resulted in heart rates ranging from 69 +/- 6 beats/min at rest to 79 +/- 14 beats/min (n = 12; P greater than 0.05). In contrast, VVIR mode pacing rates ranged from 71 +/- 11 beats/min to 115 +/- 24 beats/min (n = 17; P less than 0.05). Holter recording showed heart rates ranging from 51 +/- 6 to 110 +/- 22 beats/min during activities of normal daily living (n = 9; P less than 0.05). Passive postural tilt resulted in rates of 69 +/- 8 beats/min in the supine position increasing to 74 +/- 14 beats/min with 60 degrees upright tilt (n = 16; P greater than 0.05). With up to 5-year follow-up data, there have been no late failures of pacing but one lead showed insulation failure with over- and undersensing after 4.5 years. A number of deficiencies were identified in the prototypes leading to modifications of a subsequent generation of rate responsive pacemaker based on RV dP/dtmax. These initial data demonstrate that rate adaptive pacing based on RV dP/dtmax responds in a physiological manner. This rate responsive system is of particular interest as it is based on a beat-to-beat parameter of cardiac mechanical function.

Effect of heparin and warfarin on chronic hypoxic pulmonary hypertension and vascular remodeling in the guinea pig.

Chronic hypoxia produces pulmonary hypertension and pulmonary vascular remodeling. Heparin partially prevents the rise in right ventricular pressure and vascular remodeling in chronically hypoxic mice. To determine if this is due to the anticoagulant property of heparin or another property, we compared the effect of oral warfarin given at an anticoagulating dose (0.5 mg/kg/day) to heparin given by continuous infusion at a dose that does not prolong the partial thromboplastin time (PTT) (20 units/kg/h) on hypoxic pulmonary hypertension and vascular remodeling in the guinea pig. Normoxic control animals either untreated or treated with heparin or Coumadin were all alike in blood gases, pulmonary vascular resistance, right heart weights, and pulmonary histology. Hypoxia (10% 0(2) for 10 days) induced similar and significant increases in mean pulmonary artery (PA) pressure in both the hypoxic control and warfarin groups (19 +/- 1 mm Hg (mean +/- SEM) in both groups versus 11 +/- 0.1 mm Hg in the normoxic control group; p less than 0.05). Total pulmonary vascular resistance (TPR) was also increased from 0.041 +/- 0.002 in the normoxic control group to 0.087 +/- 0.007 and 0.071 +/- 0.003 mm Hg/ml/min/kg in the hypoxic control and warfarin groups, respectively (p less than 0.05). Whereas anticoagulation with warfarin did not protect the guinea pig from developing pulmonary hypertension, heparin markedly reduced PA and TPR (15 +/- 1 mm Hg and 0.052 +/- 0.002 mm Hg/ml/min/kg, respectively; p less than 0.05 versus hypoxic control or warfarin).(ABSTRACT TRUNCATED AT 250 WORDS)

Right heart catheterization in rats with pulmonary hypertension and right ventricular hypertrophy

Using a special Millar ultraminiature catheter pressure transducer, right ventricular functional parameters were measured in anesthetized, closed-chest rats under control conditions, during acute pulmonary hypertension and after induction of right ventricular hypertrophy. Acute i.v. infusion of noradrenaline and a brief period of hypoxia in female Sprague-Dawley rats elicited a marked increase in right ventricular systolic pressure (RVSP) and in the maximal rate of rise in right ventricular pressure (RV dp/dtmax). After 3 and 16 days of daily administrations of triiodothyronine in female Sprague-Dawley rats, all right ventricular hemodynamic parameters were enhanced along with the increase in left ventricular function. The right and left ventricles were hypertrophied, and cardiac output was increased. After 40 and 45 days subsequent to bilateral thorax irradiation of male Brown-Norway rats, RVSP and RV dp/dtmax were increased, the right ventricle was hypertrophied, while the left ventricle did not exhibit appreciable hemodynamic or morphologic alterations. Cardiac output was depressed. Thus, these two experimental models differ considerably as to the mechanism and time course of the development of right ventricular hypertrophy as well as to the participation of the left ventricle and the involvement of volume overload.

The relationship between the strength of the human heart beat and the interval between beats.

In 15 patients undergoing cardiac catheterization and pacing tests, the left ventricular (LV) pressure and its maximum rate of rise (LV dP/dt max) were measured with catheter-tip manometers. Atrial or ventricular pacing at a single steady frequency (the priming frequency) was followed by a test pulse at a varying interval (test pulse interval). In 14 subjects in whom it was examined, the contractile response after the test pulse increased with test pulse interval to reach a maximum plateau value--the optimum contractile response (OCR). In five cases, further prolongation of the test pulse interval decreased the contractile response. The optimum test pulse interval occurred at 800-900 msec. An increase in the priming frequency before the introduction of the test pulse caused a progressive increase in OCR, in contrast to the minor effects on LV dP/dt max of the control beats. Similar results were recorded in four other patients in whom contractile response was assessed from the rate of rise of right ventricular pressure. These results indicate that with tachycardia, the interval between beats is insufficient to allow maximum contractile performance (presumed to be activated by calcium ions) to develop. The true effect of increasing heart rate is only revealed by the relationship between OCR and the preceding frequency of contraction.

Right ventricular performance during ischemia: an anatomic and hemodynamic analysis.

This study in the pig was designed to characterize right ventricular (RV) contractile responses during infarction involving three areas of the heart--anteroseptal, anterolateral, and inferoseptal. Porcine coronary architecture was studied from multicolor vinyl casts. Distribution of blood supply to ventricular myocardium and papillary muscles was defined by intra-arterial dye injection. High-fidelity pressure and flow data were measured simultaneously in both ventricles following ligation of approximately equal lengths of the anterior descending, left circumflex, or posterior descending arteries. In the three groups, weight of myocardium involved by the occluded artery was comparable and there was significant depression of left ventricular performance, more pronounced in the two anterior infarcts. However, in anterolateral infarction, despite the obligatory drop in RV flow, there was no significant alteration in RV end-diastolic pressure (EDP), peak rate of rise of RV pressure (dP/dt), or time-to-peak developed dP/dt. In contrast, with both anteroseptal and inferoseptal infarctions there were significant alterations in all RV contractile parameters, at increased levels of RVEDP, signifying a primary depression in RV contractile state. With inferoseptal infarction, further occlusion of the right coronary near its origin produced a more exaggerated and selective RV contractile abnormality and, in half of the animals, varying degrees of acute tricuspid insufficiency.

Cardiovascular effects of guanazole

A rapid iv injection of guanazole, a potent antitumor drug, produces a sharp drop in arterial blood pressure, an increase in right ventricular pressure, a slight decrease in heart rate, and a rise in central and portal venous pressures. These changes are transient, lasting 5–10 min, and can be partially ameliorated by prior treatment with antihistaminic, antiserotonin, and adrenergic blocking drugs. In contrast, the slow infusion of guanazole over a 25-min period causes only a rise in right ventricular pressure and a slight drop in arterial blood pressure. These effects can be mimicked by serotonin and blocked by lysergic acid diethylamide (LSD) or propranolol. Guanazole produces a marked increase in left ventricular contractile force and a sharp drop in pump-perfusion pressure in the isolated perfused heart preparation. These changes can be blocked by LSD. Guanazole results in a decrease in pulmonary vascular resistance which is attributable not to serotonin or histamine, but to some direct action on the pulmonary bed.

Hemodynamic Consequences of Physical Training after Myocardial Infarction

The hemodynamic effects of physical training, three periods weekly for 1 to 2 months, after myocardial infarction were assessed in seven patients by cardiac catheterization at rest and during exercise. The training was followed by reduction in exercise heart rate and tension-time index as determined from brachial artery pressures. Stroke volume during exercise was enhanced. No significant change occurred in the heart volume. Left ventricular function was improved, and a significant increase in the rate of rise of right ventricular pressure occurred. These were interpreted as indicating myocardial hypertrophy, which probably through reduced compliance also accounted for increased ventricular filling pressures. Lactate in arterial blood was reduced during exercise without any change in the arteriovenous oxygen difference. Small and not significant changes occurred in vital capacity, forced expiratory volume, fasting blood sugar, and serum lipids. Concomitant with the hemodynamic changes exercise tolerance was improved. The data support the thesis that in some patients increased physical activity after myocardial infarction is followed by beneficial hemodynamic effects on the heart and possibly by increased coronary blood flow. The need for proper selection of patients and close medical supervision during training is illustrated and emphasized.

Effect of intermittent right bundle branch block on right ventricular contractility

I SOLATED right bundle branch block in man has been found to cause a slight delay in the onset of right ventricular contraction.1-5 This condition is occasionally present in an intermittent form with random alternation of normal and blocked beats6r7 In the present study right ventricular performance was evaluated in a patient with intermittent right bundle branch block. A change in the maximal rate of rise of right ventricular pressure from any given end-diastolic pressure was used as an index of a change in contractility.s-10 A preliminary report of this work has been presented.”

The use of amyl nitrite in the differentiation of Fallot's tetralogy and pulmonary stenosis with intact ventricular septum

The effect of the inhalation of amyl nitrite on the systemic and right ventricular pressures and on the systolic murmur and heart sounds has been studied in pulmonary stenosis with intact ventricular septum and Fallot's tetralogy. In pulmonary or infundibular stenosis with intact ventricular septum the inhalation of amyl nitrite results in a pronounced fall in systemic pressure and a marked rise in right ventricular pressure. The increased right ventricular pressure results in a striking increase in the loudness of the systolic murmur. After cessation of the inhalation, pressures and murmur gradually return to their original state in about 4 minutes. In Fallot's tetralogy the inhalation of amyl nitrite results in a moderate fall in both the systemic and right ventricular systolic pressures, with an increase in right-to-left shunt. The reduced right ventricular pressure results in a diminution in pulmonary flow, which is reflected by a decrease in the intensity and duration of the systolic murmur. As the effect of the vapor wears off, the pressures, murmur, and cyanosis return to the basal level, usually within 3 to 4 minutes. The reasons for these striking differences are discussed fully. The effect was similar whether the case of pulmonary stenosis or Fallot's tetralogy was mild, moderate, or severe. The amyl nitrite test is of value in settling the difficult and important diagnosis of mild (acyanotic) Fallot's tetralogy and moderately severe pulmonary or infundibular stenosis with intact ventricular septum, in cases in which the clinical, electrocardiographic, radiologic, and catheter findings may be identical. The different behavior of the systolic murmur at the bedside and of the pressures during cardiac catheterization readily distinguishes the two conditions.