Probability of Recurrence of Thrombosis in Patients with and without Factor V Leiden

Activated protein C (APC) resistance is a common risk factor for venous thromboembolism and is associated with the replacement of Arg 506 by Gin in the factor V gene (factor V Leiden). We investigated the risk of recurrence of venous thromboembolism in APC resistant patients heterozygous and homozygous for FV Leiden and compared these patient groups with a group of patients, who had a history of venous thromboembolism, but had neither APC resistance nor the FV Leiden mutation. APC resistance was determined in frozen blood samples from patients with a history of venous thromboembolism, who were not receiving oral anticoagulant (OAC) treatment. The plasma samples were collected between 1984 and 1991. Twenty-one patients in whom APC resistance was found in the stored plasma samples were reinvestigated in 1994 (5 males, 16 females, median [m] age 49 years, range 21-71 years). Twenty-one sex and age matched patients with venous thromboembolism (5 males, 16 females, age m = 50 years, range 25-73 years) investigated during the same time period who had a normal APC resistance test served as a control group. Patients with APC resistance as well as controls were reinvestigated for the presence of FV Leiden by genetic analysis in 1994. Of the 21 APC resistant patients, 5 were homozygous and 16 heterozygous for FV Leiden. Before the study entry homozygous patients had a significantly higher recurrence rate (5/5 patients) compared to the control group, in heterozygous patients (9/16) and controls (9/21) the recurrence rate was not significantly different.

The total observation time was 21 years in patients with homozygous FV Leiden, 83 years in patients with heterozygous FV Leiden and 108 years in controls, excluding the time when patients were on OAC treatment. During the observation time the recurrence rate was highest in patients with homozygous FV Leiden (9.5 % per patient per year), but was similar in patients with heterozygous FV Leiden (4.8% per patient per year) and controls (5% per patient per year). Two of five (40%) homozygous patients, 4/16 (25%) heterozygous and 5/21 (24%) controls had at least one recurrent event during the observation period. The probability for development of thrombosis in the Kaplan-Meyer-Plot analysis was not different between the three groups.

Bearing limitations of our study in mind (retrospective design, relatively small patient number) we conclude that the risk of recurrence after a thromboembolic event is not higher in patients with heterozygous FV Leiden than in patients without this mutation. Thus, it appears that the identification of heterozygous FV Leiden mutation is not an indication for long-term OAC treatment. Also, long-term OAC treatment cannot generally be recommended for homozygous patients with a single thromboembolic event. More definitive conclusions will require larger prospective studies.

Pregnancy-associated risk for venous thromboembolism and pregnancy outcome in women homozygous for factor V Leiden

INTRODUCTION

To evaluate the pregnancy-associated risk of venous thromboembolism and the risk of stillbirth and miscarriage a multicenter, retrospective and controlled study was conducted in women carrying the homozygous factor V Leiden mutation and in an agematched control group of women from the normal population.

PATIENTS AND METHODS

In 64 homozygous (median age 44 years, range 21-75 years) and in 52 control women from five different centers data on venous thromboembolism and pregnancy outcome were obtained.

RESULTS

The 64 homozygous women had in total 212 pregnancies, the 52 control women had 118 pregnancies. In homozygous women 65% of pregnancies ended with delivery of a viable infant, 15% with fetal loss (3.3% stillbirth, 12% miscarriage) and 20% by pregnancy termination. In the control women 75% of pregnancies ended with delivery of a viable infant, 12% with fetal loss (1.7% stillbirth, 10% miscarriage) and 13% by pregnancy termination. The differences were statistically not significant. Venous thromboembolism occurred significantly more often in the homozygous women, in 4.2% (9/212) during pregnancy and in 4.7% (10/212) after delivery or pregnancy termination. None of the control women had a thromboembolic episode.

CONCLUSION

Our data indicate that women with homozygous factor V Leiden have a high probability for a favorable pregnancy outcome. The increased risk for venous thromboembolism during pregnancy and after delivery would favor heparin prophylaxis during and after pregnancy in women homozygous for factor V Leiden.

Impact of the factor II: G20210A variant on the risk of venous thromboembolism in relatives from families with the factor V: R506Q mutation

OBJECTIVES

Factor V: R506Q mutation and the prothrombin G20210A variant (factor II: G20210A variant) are associated with an increased risk of venous thromboembolism (VTE). In cohorts of unrelated patients a cosegregation of both mutations has been shown to be associated with an increased risk of developing VTE. The aim of this study was to investigate the impact of the coinheritance of both mutations on the risk of VTE in relatives of symptomatic carriers of the factor V: R506Q mutation and the factor II: G20210A variant.

PATIENTS AND METHODS

Four families with 48 family members were investigated for the presence of the factor V: R506Q mutation and the factor II: G20210A mutation, and their clinical history was evaluated.

RESULTS

VTE was more frequent in family members with a combined defect (3/10; 30%) compared to those with a single mutation (1/16; 6%) or without a defect (1/12; 8%). The probability for VTE for 40-yr-old individuals with both mutations, a single mutation and no mutation was 56%, 12% and 20%, respectively.

CONCLUSIONS

These data suggest that the G to A transition at position 20210 of the prothrombin gene leads to an increase in the risk of VTE in carriers of the factor V: R506Q mutation. The determination of the factor II: G20210A variant in index patients carrying a factor V: R506Q mutation and, if present, in family members may help to identify individuals who are at high risk for VTE.

Anticoagulant dysfunction of human Arg352Trp-activated protein C caused by defective factor Va inactivation

The dysfunctional mutant R352W-protein C was found in two patients with venous thrombosis. The mutant R352A-protein C was constructed to define the contribution of charge/size of the residue at 352 on protein C (chymotrypsin numbering 187). Compared with wild type-protein C, R352W-protein C showed no difference in activation by thrombin-thrombomodulin or alpha-thrombin. However, R352W-activated protein C (APC) anticoagulant activity (aPTT assay) was reduced to approximately 65%. Although the catalytic efficiency of R352W-APC towards the oligopeptide substrate S-2366 was unperturbed, factor Va and R506Q-factor Va were not efficiently inactivated by R352W-APC compared with wild type-APC. R352A-APC showed reduced anticoagulant activity and reduced efficiency in factor Va inactivation and in factor VIIIa-inactivation in the presence of protein S. These observations suggest that the dysfunction of R352W-APC in factor Va inactivation may be one of the mechanisms leading to venous thrombosis in affected patients and that R352 plays an important role in the physiological functioning of APC.

Homocysteine levels in polycythaemia vera and essential thrombocythaemia

Patients with polycythaemia vera (PV) or essential thrombocythaemia (ET) have an increased risk of arterial and venous thromboembolic complications. Since hyperhomocysteinaemia (HHC) is a risk factor for vascular disease, we investigated the frequency of HHC in these disorders and analysed a possible association of elevated plasma homocysteine levels with vascular complications. In the cohort of 134 patients from Vienna (69 female, 65 male, median age 65.5 years, range 21-91 years) with PV (n = 74) or ET (n = 60), plasma homocysteine levels were significantly higher compared to 134 healthy controls. Median homocysteine level was 12.3 micromol/l (range 3.5-48.4 micromol/l) in patients with PV or ET and 8.9 micromol/l (range 4.8-30.5 micromol/l) in normal controls (P < 0. 0001). In addition to the 134 patients from Vienna, 48 patients (28 female, 20 male; median age 66.5 years, range 24-82) from Vicenza with PV (n = 25) or ET (n = 23) were included to evaluate the impact of HHC on the risk of thrombosis. Of 59 patients with HHC (44 from Vienna and 15 from Vicenza) 18 (31%) had a history of arterial and 10 (17%) of venous thrombosis. Of 123 patients with normal homocysteine levels, 30 (24%) had arterial and 16 (13%) had venous thromboses. The difference between the two groups was statistically not significant. Even though mild to moderate HHC occurred in a larger number of patients with PV or ET and thrombosis, it can presently not be regarded as an additional risk factor for thrombosis.

No evidence for an increased risk of venous thrombosis in patients with factor V Leiden by the homozygous 677 C to T mutation in the methylenetetrahydrofolate-reductase gene

Hyperhomocysteinemia is an established risk factor for arterial and venous thrombosis. Recently, it has been shown that a C to T mutation at nt position 677 in the methylenetetrahydrofolate-reductase (MTHFR) gene is a common cause of moderately elevated levels of plasma homocysteine in adults. In order to investigate whether the newly recognized genetic alteration in the MTHFR gene potentiates the thrombotic tendency in patients with factor V Leiden, we studied 81 unrelated patients with a history of venous thrombosis and a heterozygous factor V Leiden mutation. In addition, we analyzed 111 family members of 34 families in which the proband had a heterozygous factor V Leiden mutation. In all individuals, factor V Leiden and the MTHFR mutation were tested and the occurrence of venous thrombotic events was evaluated retrospectively. Seventy-seven healthy subjects without the factor V Leiden mutation or any other known thrombotic risk factor served as a control group. The prevalence of the homozygous MTHFR mutation was similar in index patients (10 of 81, 12%) and in the control group (10 of 77, 13%). The median age at first thrombosis in index patients was 32 years (range 22-69 years) in 10 patients with heterozygous factor V Leiden and T/T MTHFR mutation, and 34 years (range 6-72 years) in 71 patients with the factor V Leiden mutation only. In the family members, the prevalence of thrombosis was not higher in patients with factor V Leiden and +/+ MTHFR genotype than in those with only the heterozygous factor V Leiden mutation. We conclude from these data that the 677 C to T mutation in the MTHFR gene does not represent a significant additional risk factor for venous thrombosis in patients with factor V Leiden mutation.

The effect of interferon alpha on myeloproliferation and vascular complications in polycythemia vera

The effect of interferon alpha (IFN) on myeloproliferation and vascular complications was studied in 32 patients (17 female, 15 male; median age 60.5 yr) with polycythemia vera (PV). IFN therapy was initiated at a median time of 19 months after diagnosis. Ten patients were pretreated with chemotherapy in addition to phlebotomy. IFN dose was 12 megaU/wk during the first year, 9 megaU/wk during the second year and 12 megaU/wk thereafter. During IFN alpha treatment hematocrit level was 45.7% and remained at this level after the second year of treatment, compared to 46.5% before IFN. The frequency of phlebotomy before IFN was 0.49/month and dropped to 0.19/month (p <0.0005) during the first year of IFN treatment. IFN normalized high platelet and leukocyte counts in a majority of patients. The incidence of deep venous thromboses was 3.6%/yr before IFN alpha and 1.8%/yr during the first year of treatment. IFN-induced side-effects were mainly flu-like symptoms, fever, fatigue and arthralgia. In conclusion, IFN allowed the reduction of the dose of chemotherapy and decreased the need of phlebotomy. Despite improvement of hematological parameters, it is still uncertain whether IFN alpha can improve clinical symptoms in PV.

Influence of prothrombin complex concentrates on plasma coagulation in critically ill patients

OBJECTIVE

To evaluate thrombogenicity of prothrombin complex concentrates (PCCs) in critically ill patients.

DESIGN

Prospective clinical study.

SETTING

Medical intensive care unit at a university hospital.

PATIENTS

16 consecutive patients suffering from acquired deficiencies of coagulation factors and with either overt bleeding from any site or a planned invasive procedure.

INTERVENTIONS

2000 factor IX units of PCCs intravenously.

MEASUREMENTS AND RESULTS

Prothrombin time (PT), activated partial prothrombin time, fibrinogen, platelet count, plasma levels of coagulation factors II, V, VII, VIII, IX, X, antithrombin, protein C, thrombin-antithrombin complex (TAT), prothrombin fragment F(1+2), and the fibrin degradation product D-dimer were measured prior to and 1, 3, and 24 h after administration of PCCs. PT as well as coagulation factors II, VII, IX, and X, TAT, and F(1+2) showed a significant increase after administration of PCCs. All other parameters remained unchanged.

CONCLUSIONS

Administration of PCCs induces thrombin generation. No evidence for induction of disseminated intravascular coagulation in biochemical terms could be found. When rapid correction of acquired coagulation factor disturbances is warranted, the use of PCCs seems reasonable, but the elevated risk of intravascular thrombus formation should be kept in mind.

Clinical features of thrombophilia in families with gene defects in protein C or protein S combined with factor V Leiden

Twenty-nine clinically well-characterized, symptomatic index patients, 15 with protein C and 14 with protein S deficiency, in whom the genetic defect had been identified, were investigated for the presence of factor V Leiden. In six of 15 (40%) propositi with protein C and four of 14 (29%) with protein S deficiency, factor V Leiden was present. The age at first thrombosis was significantly lower (P < 0.001) in the ten propositi with a combined genetic defect (mean age 18.4 +/- 6.6 years) than in those with a single defect (mean age 32.6 +/- 10.4 years). Spontaneous occurrence, recurrence and site of thrombosis were similar in propositi with the single and the combined defect. Family studies led to the identification of a combined defect in 18 individuals from 11 families (11 propositi and 29 relatives), seven subjects had no abnormality, and in 15 a single defect was found. In individuals with a combined defect, thrombosis-free survival time was significantly shorter than in individuals with a single defect, even after exclusion of index patients. None of the seven individuals without genetic abnormality had experienced thrombosis. Our findings indicate a higher risk for development of thrombosis in individuals with a combined defect compared with those with a single defect.

Plasma exchange for treatment of thrombotic thrombocytopenic purpura in critically ill patients

OBJECTIVE

Description of diagnostic procedures, treatment modalities and intensive care management of patients with thrombotic thrombocytopenic purpura (TTP).

DESIGN

Descriptive study.

SETTING

Internal medicine Intensive Care Unit (University Hospital of Vienna).

PATIENTS

Six patients (two after allogeneic bone marrow transplantation), treated for 12 episodes of TTP.

INTERVENTIONS

Treatment with plasma exchange (fresh frozen plasma, 50-80 ml/kg per day), prednisone (0.75 mg/kg b.i.d.) and, in some cases, vincristine. Supportive therapy as needed.

MEASUREMENTS AND RESULTS

Patients were admitted to the ICU because of neurological symptoms with acute onset (42% mild, 58% severe), hemolysis and thrombocytopenia. Additional symptoms were fever (50%), bleeding tendency (50%), acute renal failure (42%) and metabolic derangement (8%). Initial laboratory values showed thrombocytopenia (median 17 G/l), hemolysis (median hemoglobin 10.0 g/dl, lactate dehydrogenase 635 U/l, reticulocyte count 175 G/l) with red cell fragmentation. Coagulation tests were normal. Respiratory assist was needed in six episodes (severe seizures, cardiopulmonary resuscitation). In patients without preexisting hematological abnormality the platelet counts exceeded 100 G/l after 3-8 cycles of plasma exchange. In patients after bone marrow transplantation, the platelet counts never exceeded 40 G/l, but the lactate dehydrogenase levels dropped significantly. The neurological symptoms disappeared in all patients and renal function normalized. One patient died before the initiation of therapy. Three patients relapsed 1-3 times between 2 weeks and 5 months after the last episode. The relapses were associated with symptoms similar to the first episode and responded promptly to plasma therapy.

CONCLUSIONS

TTP is a rare, but life-threatening disorder. It needs immediate diagnosis and has a good prognosis after adequate treatment with plasma exchange.

Spontaneous remission of acute myeloid leukemia after infection and blood transfusion associated with hypergammaglobulinaemia

Spontaneous remissions of acute myeloid leukemia (AML) have been documented in association with infection as well as blood transfusions. Activation of the immune system including an increased number of NK cells and cytokine release have been implicated in the mechanism of this phenomenon. We have observed spontaneous remissions in two patients with AML (one with a t(8;21)-positive M2, one with M5b), both occurring after infection and blood transfusions. The bone marrow showed a reduction of blast cells from 65% to 2% or 40% to 1%, respectively. Remission was accompanied by a marked polyclonal hypergammaglobulinemia in both cases (IgG values of 6420 and 2160 mg/dl, IgA of 802 and 811 mg/dl, respectively). A concomitant increase in bone marrow plasma cells was observed in both patients. Reduction of AML1/ETO PCR positivity from one-step to two-step PCR (approximately 100-fold) was documented in the patient with a t(8;21), while a regression of lymph node and skin leukemic infiltrations occurred in the patient with M5b. One patient relapsed after 4 months, at a time when his serum immunoglobulin levels had markedly decreased. The other patient is in continuous remission after 14 months. These cases suggest a potential role for a humoral immune response in the mechanism of spontaneous remission.

Oral contraceptives enhance the risk of clinical manifestation of venous thrombosis at a young age in females homozygous for factor V Leiden

In 29 patients (17 females) homozygous Arg 506 Gln mutation (FV Leiden) was identified. 25 had been investigated because of venous thromboembolism (VTE); four asymptomatic patients were found during family studies. The first VTE had occurred significantly earlier in females (median age [m] 26 years, range 17-49) than in males (m=38 years, range 21-82) (P=0.01). 12 females (80%) had taken oral contraceptives (OC, estrogen content 0.02-0.1 mg) for 6-150 months prior to thrombosis. Further triggering conditions in females were hormone replacement (n=1) and pregnancy (n=2). In 8/10 males the first VTE had occurred spontaneously--in two after surgery. The sites of VTE were deep vein thrombosis, pulmonary embolism, caval vein thrombosis and superficial thrombophlebitis. From our data we conclude that OC medication is the most important precipitating factor for VTE in females with homozygous FV Leiden.

Resistance to activated protein C (APC): mutation at Arg506 of coagulation factor V and vascular access thrombosis in haemodialysis patients

BACKGROUND

Vascular access thrombosis represents a serious problem in haemodialysis patients. Therefore identification of relevant thrombotic risk factors is clinically valuable. Resistance to activated protein C (APC) was recently identified as a new thrombophilic defect which is caused by a single point mutation in the factor V gene. Whether this mutation predisposes to vascular access thrombosis is unknown.

METHODS

The presence of factor V Leiden (mutation at nucleotide position 1691 of the factor V gene) was determined by polymerase chain reaction (PCR) analysis in 152 haemodialysis patients from all three haemodialysis units of the University Hospital of Vienna. In 61 patients (54 without mutation, 7 with heterozygous mutation) resistance to APC was evaluated. One hundred-seven individuals without renal failure (57 negative for factor V Leiden, 50 heterozygous subjects) served as controls. Haemodialysis patients with heterozygous factor V Leiden mutation were carefully investigated for thrombotic complications of vascular access, other thromboembolic events and additional putative thromboembolic risk factors.

RESULTS

Seven of 152 (4.6%) patients were heterozygous carriers of factor V Leiden. The mean APC resistance ration in heterozygous dialysis patients was 2.31; in the 50 heterozygous controls the ratio was 2.02. The mean APC ratio in haemodialysis patients without mutation was 3.53 in contrast to 2.95 in the control group. Not one of the seven heterozygous haemodialysis patients suffered from vascular access thrombosis of inexplicable origin. Three patients remained totally free of access thrombosis from onset of haemodialysis treatment. In four of seven patients nine events of thrombosis of the vascular access occurred, but were due to anatomical stenosis in each case. In six permanent central venous catheters no episode of occlusion or reduced blood flow requiring thrombolytic therapy was observed. Family history with regard to thrombotic events was negative in all seven patients. No thromboembolic complication occurred during 13 periods of immobilization, in the course of six pregnancies and during oral contraception.

CONCLUSIONS

The heterozygous carrier status for factor V Leiden does not appear to represent a risk factor for vascular access thrombosis in haemodialysis patients. This is possibly due to the fact that the functional APC activity is high and in heterozygous haemodialysis patients APC resistance ratios are very close to the normal range. However, it cannot be excluded that a homozygous factor V mutation represents an increased risk for shunt thrombosis. Therefore patients suffering from repeated and/or inexplicable shunt thrombosis should be tested for the factor V mutation to evaluate the effect of a homozygous mutation.

Probability of recurrence of thrombosis in patients with and without factor V Leiden

Activated protein C (APC) resistance is a common risk factor for venous thromboembolism and is associated with the replacement of Arg 506 by Gln in the factor V gene (factor V Leiden). We investigated the risk of recurrence of venous thromboembolism in APC resistant patients heterozygous for FV Leiden and compared these patient groups with a group of patients, who had a history of venous thromboembolism, but had neither APC resistance nor the FV Leiden mutation. APC resistance was determined in frozen blood samples from patients with a history of venous thromboembolism, who were not receiving oral anticoagulant (OAC) treatment. The plasma samples were collected between 1984 and 1991. Twenty-one patients in whom APC resistance was found in the stored plasma samples were reinvestigated in 1994 (5 males, 16 females, median [m] age 49 years, range 21-71 years). Twenty-one sex and age matched patients with venous thromboembolism (5 males, 16 females, age m = 50 years, range 25-73 years) investigated during the same time period who had a normal APC resistance test served as a control group. Patients with APC resistance as well as controls were reinvestigated for the presence of FV Leiden by genetic analysis in 1994. Of the 21 APC resistant patients, 5 were homozygous and 16 heterozygous for FV Leiden. Before the study entry homozygous patients had a significantly higher recurrence rate (5/5 patients) compared to the control group in heterozygous patients (9/16) and controls (9/21) the recurrence rate was not significantly different. The total observation time was 21 years in patients with homozygous FV Leiden, 83 years in patients with heterozygous FV Leiden and 108 years in controls, excluding the time when patients were on OAC treatment. During the observation time the recurrence rate was highest in patients with homozygous FV Leiden (9.5% per patient per year), but was similar in patients with heterozygous FV Leiden (4.8% per patient per year) and controls (5% per patient per year). Two of five (40%) homozygous patients, 4/16 (25%) heterozygous and 5/21 (24%) controls had a least one recurrent event during the observation period. The probability for development of thrombosis in the Kaplan-Meyer-Plot analysis was not different between the three groups. Bearing limitations of our study in mind (retrospective design, relatively small patient number) we conclude that the risk of recurrence after a thromboembolic event is not higher in patients with heterozygous FV Leiden than in patients without this mutation. Thus, it appears that the identification of heterozygous FV Leiden mutation is not an indication for long-term OAC treatment. Also, long-term OAC treatment cannot generally be recommended for homozygous patients with a single thromboembolic event. More definitive conclusions will require larger prospective studies.

Lethal Waterhouse-Friderichsen syndrome in posttraumatic asplenia

We herein report a case of fulminant lethal Waterhouse-Friderichsen syndrome in an elderly female patient seven years after posttraumatic splenectomy. In contrast to various reports, this patient had not been vaccinated against Streptococcus pneumoniae, Neisseria meningitidis, or Haemophilus influenzae, respectively, although infections with these microorganisms are known to cause the main lethal diseases in asplenic patients. Again, we recommend obligatory vaccinations against the mentioned bacteria for it is known that this decreases the risk of fatal septic events in these patients. To optimize prevention, it is imperative to vaccinate patients undergoing splenectomy before discharge from hospital.

Emergency intubation with the Combitube in two cases of difficult airway management

The airway was managed successfully in two cases of difficult intubation using the Combitube, a new device for emergency intubation, which combines the functions of an oesophageal obturator airway and a conventional endotracheal airway. One patient could not be intubated due to lockjaw; in the other patient, the vocal cords could not be seen because of continued vomiting. The cases illustrate the benefit of the Combitube during emergency intubation for different problems and its effectiveness as an alternative to traditional intubation techniques.

[Bronchiolitis obliterans organizing pneumonia with acute respiratory insufficiency]

A 22-year-old woman was hospitalized because of fever of 39 degrees C and increasing dyspnoea. The chest radiograph demonstrated coarse confluent opacities bilaterally. Despite antibiotic treatment the condition deteriorated acutely after 2 days. All efforts to find an infectious agent, including immunological tests, were unsuccessful. Artificial ventilation became necessary because of increasing respiratory failure with an arterial oxygen partial pressure of 56 mm Hg, CO2 of 41 mm Hg and a respiratory rate of 60/min. Histological examination of a transthoracic lung biopsy revealed bronchiolitis obliterans organizing pneumonia, which was treated with prednisolone. The initial dose was 500 mg/d, gradually reduced to 12.5 mg/d over 2 weeks. The clinical and radiological findings improved markedly after 2 days and the patient discharged herself after 3 weeks and there was no follow-up.

Magnetic resonance imaging of the heart during positive end-expiratory pressure ventilation in normal subjects

OBJECTIVES

Magnetic resonance imaging was used to assess the effects of ventilation with positive end-expiratory pressure (PEEP) on cardiac volumes, especially on atrial volumes as well as to determine semiquantitative measurements of spatial interactions between heart, lungs and chest.

DESIGN

Prospective study with healthy volunteers undergoing mechanical ventilation with different levels of PEEP during magnetic resonance imaging.

SETTING

Magnetic resonance unit, Institute of Diagnostic Imaging, Rudolfinerhaus Hospital.

SUBJECTS

Twelve healthy volunteers.

INTERVENTIONS

Volunteers were imaged, using a multislice-multiphase technique during spontaneous breathing and with PEEP values of 0, 7, and 15 cm H2O.

MEASUREMENTS AND MAIN RESULTS

Atrial as well as ventricular volumes, chest diameters, and midventricular contact between the heart and anterior chest wall were determined on transverse-oblique sections. Atrial volumes showed a progressive decline beginning at a PEEP of 7 cm H2O. Diastolic filling of both ventricles was reduced. A PEEP level of 15 cm H2O induced a significant increase in the sagittal-oblique but not in the transverse-oblique chest diameter. PEEP values of 7 and 15 cm H2O shortened the length of the midventricular contact between the heart and anterior chest wall.

CONCLUSIONS

Left and right ventricular end-diastolic volumes and stroke volumes decreased significantly during ventilation with PEEP at 15 cm H2O, as did end-systolic atrial volumes. Volume changes in association with changes of chest and heart configuration suggest external cardiac compression by the expanding lungs. Furthermore, this study illustrates the feasibility of magnetic resonance imaging in mechanically ventilated patients.