Management of High-Risk Pulmonary Thromboembolism Using Conventional Catheter Devices: A Case Report

Introduction

Clinical studies have provided robust evidence on the effect of risk stratification–based treatments in patients with acute pulmonary thromboembolism (PTE) [1,2]. For instance, initiating anticoagulant therapy and discharging patients home can be appropriate for low-risk PTE, whereas intensive care is required for high-risk PTE. However, the mortality of patients with high-risk PTE who have hemodynamic and respiratory instability despite anticoagulation therapy is still high. High-risk PTE is the third most frequent cause of cardiovascular death, and approximately 65% of patients with high-risk PTE die in the acute phase [3].

According to international guidelines, there are several options of therapeutic intervention for high-risk PTE, such as veno-arterial extracorporeal membrane oxygenation (ECMO), surgical thrombectomy, and catheter-directed therapies (CDTs), including mechanical aspiration, thrombolysis, and mechanical fragmentation [1,3–5]. Although ECMO is widely known and used as the therapeutic option for high-risk PTE, its effectiveness for survival is still controversial [6,7]. Surgical thrombectomy, which is performed under cardiopulmonary bypass, is not widely practiced because the procedure is highly invasive and complex [8].

For patients with high-risk PTE, CDT is reported as the less invasive and effective therapeutic option and is recommended in the guidelines [1,5]. Although many reports and reviews demonstrate the efficacy and safety of CDT using the specialized devices for thrombus aspiration and thrombolysis, CDT using these devices has not been widespread [3,9], as they are expensive and typically not available in general hospitals. Several reports demonstrate that CDT using conventional devices, such as the guiding catheter for percutaneous transluminal coronary angioplasty (PTCA) and pigtail catheter, is also effective. However, few reports indicate the technical guidance and limitations of CDT using these conventional devices.

We report a case in which a patient with high-risk PTE was successfully rescued by CDT using the conventional devices that are commonly used for catheter intervention. We also discuss the technical aspects of the procedure and its limitations.

Case Report

CLINICAL COURSE:

A 72-year-old woman who had no past medical history and was taking no medications had been admitted to a nearby hospital for a right femoral neck fracture 10 days before. After conservative therapy with subcutaneous injection of heparin, the patient was planned to receive surgery. On the day of surgery, the patient suddenly experienced cardiogenic shock right before anesthesia; the oxygen saturation (SpO₂) decreased below 70%, systolic blood pressure (BP) decreased below 70 mmHg, and heart rate was below 40 beats per min.

First, cardiopulmonary resuscitation including endotracheal intubation was performed with the administration of adrenalin. Then, the patient was transferred to the South Miyagi Medical Center, Japan. At the time on arrival, her BP was 66/46 mmHg, heart rate was 141 beats per min, and Glasgow Coma Scale score was 6 (E1M1V4). Blood gas analysis with the patient on the support of a respirator showed metabolic acidosis: pH of 7.08, PaO2 of 218 mmol/L, PaCO2 of 46 mmol/L, lactate level of 7.0 mmol/L, and HCO3 of 13 mmol/L. Contrast-enhanced computed tomography (CT) showed massive thrombus at the right interlobal pulmonary artery (PA), and blood clots were found in the bilateral lower periphery (Figure 1A, 1B). Also, deep vein thrombus was found in the right superficial femoral vein and popliteal vein. We diagnosed high-risk PTE with class V of the Pulmonary Embolism Severity Index score, because of deep vein thrombus probably formed during bed rest. Laboratory test results were as follows: D-dimer level of 26, activated partial thromboplastin time of 81 s, blood urea nitrogen level of 31 mg/dL, serum creatinine level of 1.6 mg/dL, and B-type natriuretic peptide level of 391 pg/mL. Furthermore, ultrasound echocardiography showed the increase of right ventricular (RV) afterload with RV enlargement with a D-shaped left ventricle, tricuspid regurgitation pressure gradient of 40 mmHg, RV to left ventricular (RV/LV) ratio of 1.0, systolic-to-diastolic ratio of the hepatic vein of 0.55, and pulmonary vascular resistance of 5.7 Wood units.

We started administration of 0.4 μg/kg/min of adrenaline, 0.4 μg/kg/min noradrenaline, and 5 μg/kg/min of dobutamine to keep the systolic BP over 60 mmHg. We also systemically administered 160×10⁴ IU/60 min of recombinant tissue plasminogen activator (monteplase) and 20 000 U/day of heparin. Furthermore, we administrated extracellular fluid and packed red blood cell for augmentation of forward cardiac output. However, the systolic BP decreased to below 60 mmHg, and blood gas analysis still showed metabolic acidosis, with continuing anuria on day 2. These clinical findings implied conservative medical therapy was insufficient, and interventional therapy should be performed to rescue the patient. We then decided to perform CDT.

ESTABLISHMENT OF THE CDT SYSTEM:

After confirming that active clotting time was 340 s, a 9-Fr short sheath (Medi-kit) was inserted in the right femoral vein, and a 5-Fr wedge-pressure catheter (Gadelius) was advanced into the PA with support of a 0.035-inch, 260-cm hydrophilic guidewire (Radicocus, Termo). The measured PA pressure was higher than 30 mmHg. Next, we tried to advance the 9-Fr guiding sheath (Super Arrow-Flex Sheaths, 80 cm, Teleflex) into the right PA with support of the previously placed 0.035-inch guidewire. However, the guidewire did not provide sufficient support to advance the 9-Fr guiding sheath from the right ventricle to the right PA; therefore, support with a stiff-shaft was required. We selected a 0.035-inche guidewire with a harder shaft and flexible soft tip (EGoist interventional guide wire, standard 260 cm, Medico’s Hirata), which was ordinarily used for endovascular aortic aneurysm repair (EVAR). Due to the strong support of this guidewire, we successfully advanced the 9-Fr guiding sheath from the right ventricle to the right PA, establishing the system of the CDT (Figure 2A).

THROMBECTOMY USING PTCA GUIDING CATHETER:

PA angiography showed thromboembolism at the right interlobal PA (Figure 2B). We inserted a 8-Fr PTCA guiding catheter (Mach 1 JR4, coronary guide catheter, Boston Scientific) through the 9-Fr guiding sheath to the right interlobal PA for thrombectomy. After connecting a Y-connector (OKAY II, NIPRO) to the PTCA guiding catheter, we performed thrombectomy by applying negative pressure repeatedly with a 30-mL vacuum syringe (VacLok, Merit Medical) (Figure 2C). As a result, we successfully aspirated thrombi (Figure 2D) and confirmed the angiographical translucency at the distal portion of the right distal PA.

THROMBOLYSIS AND THROMBUS FRAGMENTATION USING PIGTAIL CATHETER:

We changed the PTCA catheter to a 6-Fr pigtail catheter (Goodtec) to perform local thrombolysis and mechanical fragmentation (Figure 2E). After a bolus injection of 80×104 IU of monteplase from the tip of the pigtail catheter to dissolve the thrombus, mechanical fragmentation was performed by rotating the pigtail catheter manually. Immediately after the administration of monteplase, the patient’s vital signs improved, with BP increasing to 100/77 mmHg, and SpO2 increasing to 94%.

After performing thrombus fragmentation, however, the hemodynamics gradually deteriorated, with BP 69/44 mmHg and SpO2 70%. A contrast delay was observed in the far distal portion of the target PA by tip injection from the pigtail catheter, suggesting that distal thrombosis had occurred as a result of excessive manual fragmentation, which may have deteriorated the hemodynamics. To recover the hemodynamics, sodium bicarbonate and saline were rapidly administrated intravenously. As BP increased above 80 mmHg due to rapid fluid administration, the escalation to ECMO was avoided. Given the improvement of distal PA perfusion on angiography, CDT was completed, although numerous thrombi remained at the lesion site (Figure 2F).

POSTOPERATIVE COURSE:

After the procedure, continuous hemodiafiltration was performed to correct acidemia and remove body fluid. On day 3, the hemodynamics and acidemia improved, with BP increasing to above 100 mmHg, and SpO2 to above 98%. On day 4, diuresis occurred spontaneously. On day 5, the patient was weaned off dialysis and ventilation. Furthermore, we changed the anticoagulant therapy from heparin to a direct oral anticoagulant. Ultrasound echocardiography on day 6 showed a marked reduction in RV overload, with resolution of the D-shaped left ventricle. The tricuspid regurgitation pressure gradient was 30 mmHg, the RV/LV ratio was 0.9, the hepatic vein systolic-to-diastolic flow ratio was 1.47, and pulmonary vascular resistance was 1.7 Wood units. CT showed no thrombus at the right PA (Figure 1C, 1D). Furthermore, pulmonary perfusion scintigraphy showed little evidence of lung infarction. After extubation and rehabilitation, the patient underwent femoral replacement and was discharged ambulatory. As no pulmonary thrombus or deep vein thrombosis was detected on CT at 3, 6, and 12 months after the event, direct oral anticoagulant therapy was discontinued.

Discussion

ESTABLISHMENT OF THE CDT SYSTEM USING COMMON DEVICES:

To advance the guiding sheath, such as the Super Arrow-Flex 9-Fr sheath, to the PA is sometimes difficult because of higher PA pressure than usual and enlargement of the right ventricle in patients with high-risk PTE. In our case, we used a stiff wire with a flexible soft tip, as used in cases of EVAR, expecting the 9-Fr guiding sheath to enable the advancement to the right distal PA. This resulted in the establishment of the CDT system. Thus, if introduction of the guiding sheath is difficult due to pulmonary hypertension and right ventricle deformation, we recommend using the strong shaft wire for EVAR to establish the CDT system; however, careful maneuvering of the wire is necessary.

LIMITATION OF THROMBECTOMY USING PCTA GUIDING CATHETER:

Several aspiration systems, such as the Indigo Aspiration system (Penumbra) and Flow Triever System (Inari Medical), have been developed and reported to have an extraordinary effect in removing massive pulmonary thrombi [3,9]. In our case, we adapted conventional devices, such as the PTCA guiding catheter, which has been reported to be effective for aspiration [15]. We aspirated the thrombus using an 8-Fr PTCA guiding catheter by applying negative pressure manually, consequently aspirating a small amount of thrombus but not enough for pulmonary reperfusion. Therefore, the ability of manual thrombectomy to remove enough thrombus can be limited, and additional procedures, such as catheter-guided thrombolysis and fragmentation, should be additionally performed.

CATHETER-GUIDED THROMBOLYSIS AND MECHANICAL FRAGMENTATION:

Catheter-guided thrombolysis and fragmentation are reported to offer a synergistic effect to remove thrombus in high-risk PTE [3,9]. These procedures can break down and redistribute a central thrombus in the PA to the periphery, resulting in creating a greater surface area. Although ultrasound-assisted thrombolysis is reported to be effective and safe on catheter-directed thrombolysis [3], in the present case, we could not prepare such a thrombolysis-specialized device. We used a 6-Fr pigtail catheter and performed intrapulmonary injection of 80×104 IU of monteplase and further performed mechanical fragmentation by rotating the pigtail catheter in the residual thrombus, as previously reported [16,17]. However, in the present case, this procedure resulted in deterioration of hemodynamics and oxygenation. This re-exacerbation was likely caused by abnormal pulmonary microcirculation resulting from distal embolism of fragmented thrombi [18].

In general, the volume of the peripheral circulatory bed is known to be approximately twice as large; however, the vascular reserve in patients with PTE is decreased due to blood flow obstruction caused by local vasoconstriction [3]. Based on this pathophysiological mechanism, the pulmonary microvascular reserve in our case might have decreased. The distal embolism caused by fragmented thrombi could then have further deteriorated pulmonary circulation, resulting in hemodynamic breakdown. Thrombolysis-specialized devices, such as the Uni-Fuse infusion catheter (Angiodynamics), EKOS endovascular system (Boston), and Cragg-McNamara Micro therapeutic infusion catheter (Medtronic), may be able to dissolve or finely fragment the thrombus, leading to the enhanced effectiveness of CDT. On the other hand, local delivery of thrombolytics and mechanical fragmentation using a pigtail catheter may be limited in their ability to achieve fine thrombus fragmentation. Therefore, we should be aware that excessive manual fragmentation can cause distal embolism, resulting in the deterioration of hemodynamics. To prevent the development of distal embolism, the pigtail catheter should be rotated gently while continuously monitoring patient vital signs.

Conclusions

We rescued a patient with high-risk PTE using hybrid CDT with conventional devices. We describe some procedural limitations of the hybrid CDT we encountered, most of which could be resolved. The remaining limitation was the technique for thrombus fragmentation, which requires further refinement for better outcomes