Fig. 31.1
Practice print materials: Information brochure and sample page. UPSG Risk Stratification Booklet. Referring Physician Quarterly Mailer Folder. Annual Heart and Brain Symposium Program. SPACE Urgent Referral Program Patient Information Folder
Physician Education Programs
Utah PFO Study Group (UPSG)
This regional group of cardiologists, neurologists, and neuro-imaging specialists was organized to provide agreement about the application of existing information in treating our patients. Surgical PFO closure had long been an accepted treatment option in our community and device closure therefore seemed a reasonable option to many. However, clinicians found themselves in a treatment paradox with conflicting opinions. Accordingly, UPSG developed consensus documents for FOD definition, risk stratification, migraine and PFO, and OLU. The documents supported by evidence-based bibliographies are available at the USPG website; www.utahpfostudygroup.com [25]. The group has supported clinical research activities including RCT and an annual regional meeting.
Referring Physician Education
To aid medical care givers in understanding our approach to diagnosis and closure we developed several approaches: Fig. 31.1 shows the printed versions of assistance available to providers: (1) a PFO Information pamphlet, (2) a quarterly provider mailer describing recent advances, (3) UPSG reference materials, (4) an annual CME-accredited, regional Heart and Brain Symposium, and (5) an urgent evaluation program (SPACE) providing brain imaging, TCD/TTE testing, and neurology consultation within 48 h.
It was also necessary for us to develop targeted specialty communications because the unusual PDE presentations of some patients led them to physicians who might be unfamiliar with PFO and its complications. For example, patients with visual disturbance due to posterior circulation stroke or TIA frequently might see an ophthalmologist or optometrist. Stroke/TIA imbalance patients see ENT or balance center physicians. Women with TIA symptoms associated with pregnancy or oral contraceptives seek obstetrical or gynecological care.
For cardiologists interested in becoming more directly involved in PFO and ASD closure, we offered Visiting Physician 2-day office shunt diagnosis and implantation training.
Testing
Transcranial Doppler (TCD)
Power M-mode TCD is in our experience the best means of detecting and importantly, quantifying RLS, the fundamental need for evaluating FOD. Figure 31.2 shows the logarithmic Spencer grading scale. TCD is inexpensive, mobile and office-based, reproducible for serial studies, and provides the best physiologic information for provocation. Although Valsalva is performed in all patients, we rely on manometer-calibrated respiratory strain as the most reproducible method. Rest RLS, indicating greater duration of shunt and increased PDE risk, increases in 40 % of patients with upright posture which is best evaluated by TCD [26]. Figure 31.3 demonstrates the appearance of severe, Grade 5 resting shunt with upright posture in a patient with severe Valsalva-only RLS when supine. Since PFO by definition are competent defects, such severe continuous shunting is more compatible with an ASD diagnosis. The presence (or absence) of the auditory and visual signals arising from the TCD headset after venous contrast injection is compelling to patients undergoing diagnosis and follow-up after implantation. In our experience, transient neurologic symptoms occur during or immediately after TCD in nearly one-third of patients with shunt and neurological symptoms are four times more likely in those with a history of migraine headache. These observations raise the possibility of using such induction of symptoms as a predictor of benefit of closure.
Fig. 31.2
Spencer Logarithmic Shunt Grade for Trivial Shunt (Grade I–II), Intermediate Shunt (Grade III–IV), Severe Shunt (Grade V–V+). TNTC, “ too numerous to count”
Fig. 31.3
The effect of upright posture on the severity of rest shunting. Severe shunting is present with strain. Rest shunt increases from Grade 0 to severe Grade V+ with standing
Transthoracic Echocariography (TTE)
TCD does not provide anatomic cardiac information. In healthy adults, modern TTE with bubble contrast complements TCD and provides good and adequate morphologic information in selecting patients for closure.
Transesophageal Echocardiography (TEE)
In our experience TEE is poorly suited as a screening or management test for adults with shunt syndromes because of cost, inconvenience, discomfort, risk, and poor shunt definition. We reserve its use to patients with complex anatomic issues or indeterminate results. However, in unusual circumstances where patients are considered at high risk for PDE, intracardiac echocardiography (ICE) and ad hoc closure may be preferred over TEE.
Magnetic Resonance Brain Imaging (MRI)
An abnormal MRI is a common reason for referral to us for cardiac and shunt evaluation after negative evaluation elsewhere. For example, negative evaluations for balance or visual disturbance lead to MRI to identify a central cause. As serial studies have demonstrated that most T2 lesions on MRI evolve from diffusion positive lesions we do not simply consider these changes as being “non-specific” [25]. We require brain MRI and MRA as well as neurological consultation in all patients.
Risk Stratification
Basic to all therapeutic medical decision making is the ability to define relative risk and thereby choose appropriate therapy. Over a decade ago, the Lausanne Study investigators, after evaluating 140 young patients with PFO and stroke made the following observations which remain relevant today:
In summary, our study shows that the first brain event in patients with PFO may often be devastating, as one-half of patients suffered a severe initial stroke. On the other hand, the overall risk of stroke seems rather low. The demonstration of factors associated with an increased risk of recurrence in our study and other studies suggest that high risk patients with PFO exist. Further attempts to better delineate the factors associated with a higher risk of stroke seem necessary before launching a clinical trial because of the high number of patients with a low recurrence risk who would be included in a trial randomizing non-selected patients with PFO and stroke [27].
While recent PFO RCT have limited risk evaluation to a crude measure of shunt severity and atrial septal aneurysm (ASA), a large number of factors associated with increased PFO risk have been described. We developed a risk stratification protocol for selecting high risk patients for PFO closure and a UPSG consensus statement and bibliography document supporting this approach [25]. Figure 31.4 shows the Stroke Risk Stratification Worksheet we used to assess relative stroke risk related to compelling neurological symptoms, shunt severity by TCD and TTE (emphasizing rest shunt), brain MRI, atrial septal aneurysm, migraine and coagulation issues including venous thrombosis, pulmonary embolism, hyper-coagulation disorders, planned pregnancy, and oral contraceptive use, etcetera. We adopted a risk stratification approach of only implanting patients with severe shunt. Most non-TCD risk stratification studies are of questionable value since the presence and severity of PFO cannot be defined by these studies using un-validated and antiquated methods. Figure 31.5 demonstrates the logarithmic shunting seen using power m-mode TCD and the distribution of our published and reported 2,700 patients. If one accepts any reliability of the level of shunting reported in PFO/stroke prevalence studies or RCT, then on average, 66 % of these patients overall have trivial or no shunt; less than 20 bubbles.
Fig. 31.4
Program Risk Stratification Worksheet used to define relative risk of stroke using evidence-based risk factors
Fig. 31.5
Spencer Logarithmic Shunt Grading showing TCD display as seen for different levels of shunt and the logarithmic (red curve) nature of shunting. USPG = the severity of shunting in 2,700 Program patients (blue). The percentage of patients in PFO studies with low level shunting demonstrates population differences between clinical practice and published studies (magenta). See text
Implant Procedure
Our implantation procedure has been previously described using ICE imaging [28]. For device selection, we perform a septal deformation Forbes’ procedure using a simple balloon-tipped pulmonary capillary wedge catheter. As shown in Fig. 31.6, this manipulation, in vivo, mimics the probing methods used in necropsy specimens to evaluate FOD. Panels (b) and (c) show diagrammatic and ICE images which mimic necropsy defect probing in panel (a). These panels demonstrate a restrictive, true PFO defect which we preferentially close with central pin devices. Similarly, panels (e) and (f) show in vivo balloon reduction of a redundant, reducible septum primum similar to the specimen probe reduction in panel (d). These non-restrictive, deformable defects are usually closed with central occluding devices in our program. We have previously demonstrated lower residual shunt with this approach [28]. Although commonly considered PFO, this non-restrictive type of defect meets necropsy (Blom 1b or Tandon Class 1) criteria for secundum ASD [25].
Fig. 31.6
In vivo FOD evaluation by balloon pull-back technique. (a) LA view of probe in restrictive FOD defect. (b) Balloon pull-back showing primum restriction. (c) ICE in vivo FOD evaluation by pull-back mimicking panel a (d–f: Reduction of mobile septum primum by pull-back technique. See text)
The passage of bubbles through the pulmonary bed, which is common, may contribute to misinterpretation of diagnostic shunt studies. Figure 31.7 demonstrates a simple procedure for defining pulmonary bed bubble passage. During the implant procedure, ICE imaging of the left atrium and pulmonary veins detects bubble appearance from bilateral, selective pulmonary artery contrast bubble injections [29]. When a septal defect cannot be defined, this technique is useful in detecting pulmonary AVM. Conversely, a negative combined ICE/pulmonary injection study in a patient with severe RLS by diagnostic study would prompt further septal evaluation. In patients with high pulmonary conductance of bubbles and a septal defect, this method helps in the post-implant evaluation of device residual shunting.
