Heart issues; Reaction from Pfizer 4th booster; Low blood pressure; Low heart rate; Atrial fibrillation; This is a solicited report received from contactable reporter(s) (Consumer or other non HCP and Other HCP). The reporter is the patient. Other Case identifier(s): UNT-2022-012541.  An 85-year-old female patient received BNT162b2 (BNT162B2), as dose 4 (booster), single (Batch/Lot number: unknown) for covid-19 immunisation; treprostinil sodium (TYVASO), on 21Jun2019 (Batch/Lot number: unknown) and as 18 ug, 4x/day (Lot number: 2102169, Expiration Date: 31Aug2023) for pulmonary arterial hypertension. The patient's relevant medical history included: "Pulmonary arterial hypertension" (ongoing). Concomitant medication(s) included: XARELTO. Vaccination history included: Covid-19 vaccine (First Dose), for Covid-19 Immunization; Covid-19 vaccine (Second Dose), for Covid-19 Immunization; Covid-19 vaccine (Third Dose), for Covid-19 Immunization. The following information was reported: ATRIAL FIBRILLATION (medically significant) with onset 04Jun2022, outcome "unknown"; HYPOTENSION (non-serious) with onset 04Jun2022, outcome "unknown", described as "Low blood pressure"; HEART RATE DECREASED (non-serious) with onset 04Jun2022, outcome "unknown", described as "Low heart rate"; IMMUNISATION REACTION (non-serious) with onset 04Jun2022, outcome "unknown", described as "Reaction from Pfizer 4th booster"; CARDIAC DISORDER (non-serious) with onset 05Jun2022, outcome "unknown", described as "Heart issues". The events "atrial fibrillation", "heart issues", "reaction from pfizer 4th booster", "low blood pressure" and "low heart rate" required emergency room visit. The patient underwent the following laboratory tests and procedures: Blood pressure measurement: low; Heart rate: low. The action taken for treprostinil sodium was unknown. The reporter's assessment of the causal relationship of "atrial fibrillation", "heart issues", "low blood pressure" and "low heart rate" with the suspect product(s) BNT162b2 was not provided at the time of this report. Since no determination has been received, the case is managed based on the company causality assessment. The reporter considered "reaction from Pfizer 4th booster" related to BNT162b2. Case Description: He began therapy with IH Tyvaso (treprostinil sodium, concentration of 0.6 mg/ml) delivered by Tyvaso Inhalation Device (TD-300/A), on 21Jun2019 for primary pulmonary arterial hypertension. The current dose was reported as 18 ug (3 breaths), four times a day (QID) via inhalation (IH) route. On 05Jun2022 (yesterday), 2 years 11 months and 16 days after initiating Tyvaso, the patient went to the emergency room due to heart issues (cardiac disorder).The reporter did not provide causality for the event of cardiac disorder. Co-suspect included Pfizer BioNTech COVID-19 vaccine (tozinameran). On 04Jun2022, 2 years 11 months and 15 days after initiating Tyvaso the patient had emergency room visit for reaction from Pfizer 4th booster (immunization reaction), threw into atrial fibrillation (atrial fibrillation, medically significant), low blood pressure (hypotension), and low heart rate (heart rate decreased). Action taken with Tyvaso was not reported for the events of atrial fibrillation, immunization reaction, hypotension, and heart rate decreased. At the time of reporting, the outcome of atrial fibrillation, immunization reaction, hypotension, and heart rate decreased was unknown. The reporter did not provide causality for the events of atrial fibrillation, immunization reaction, hypotension, and heart rate decreased. The reporter's causality for the event of immunization reaction was considered as possibly related to Pfizer BioNTech COVID-19 vaccine.  Case Comment/Senders Comment: The company has assessed the serious adverse event of atrial fibrillation as not related to inhaled treprostinil and TD300/A device. The event was more likely related to the underlying PAH. Remodeling of the right ventricle and the right atrium appears to generate the underlying arrhythmogenic substrate in patients with PAH. Other Relevant History, Including Preexisting Medical Conditions (e.g., allergies, race, pregnancy, smoking and alcohol use, hepatic/renal dysfunction, etc.): Ongoing, Current Condition, Pulmonary arterial hypertension  No Follow-up attempts are possible. Information about lot/batch cannot be obtained. No further information is expected.; Sender's Comments: Based on the information provided in the narrative , a possible contributory role of the suspect vaccine  to reported event of Atrial fibrillation, cardiac disorder,  hypotension,  heart rate decreased   cannot be excluded. The case will be reassessed once additional information is available. However,the event of   immunization reaction  is assessed as related to suspected vaccine  The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to regulatory authorities, Ethics Committees, and Investigators, as appropriate.