I am listening to the rhythm of my beating heart.

I am lying on my left side atop an uncomfortable exam table wearing a breezy paper gown that gapes open in the front like a J-Lo Oscar dress. Sort of. As I concentrate on the pulsations, I can almost ignore the fact that a woman I have never met is wielding a freezing cold wandlike instrument between my breasts in an attempt to pick up Doppler signals from my ticker.

Humiliating midlife experience number 35: the echocardiogram.

Fifteen minutes ago, I walked into this darkened exam room, where the sonographer and her female assistant introduced themselves and asked me to strip to the waist and don the pulpy vest. Expecting them to get up and leave the room to allow me a modicum of privacy, I said in my most pleasant, perfect-patient way, “OK.” When it became apparent they didn’t plan to budge from their chairs, my first thought was, “Oh well, we’re all girls here,” and I dutifully did what I was told.

My second thought was how I never would have been so nonchalant about disrobing in front of two strangers 20 years ago. I’ve come a long way, baby.

(My third thought was wondering how much these gals were pulling down a year and with what kind of benefits. Because with each new professional I meet these days, I find myself scoping out career options for my vocationally clueless college-age kids. Note to self: Google “sonographer annual salary” after this is over.)

I am in this precarious position because two weeks ago, during a routine physical, my doctor heard some kind of murmur in my chest. Considering my recent high blood pressure diagnosis, she scheduled this ultrasound “just to be sure nothing’s wrong.” “OK,” I said, just as pleasant as can be.

Ever the obedient subject, I do everything the sonographer asks. “Lie on your back. Hold your breath. Roll on your side. Now cough. And again. Now lean forward. Hold it :” “OK,” I reply, my voice dripping with affability.

I am no stranger to ultrasound technology. Years ago, the sonogram was the highlight of my prenatal check-ups. I still remember the first time I heard my son’s urgent little heartbeat amplified through my obstetrician’s boom box. At 150 beats per minute, it was like the rapid-fire bass line to a frenetic techno dance tune. Bwamp-bwamp-bwamp-bwamp-bwamp-bwamp-bwamp …

My own cardiac cadence, at half the tempo, sounds more like one of those laid-back, pimped-out rides cruising down the street, blaring and bouncing with turbo-powered amps and subwoofers. BAH-woomp, bwoomp. BAH-woomp, bwoomp. Hip-hop for the fish oil set. (“It has a nice beat, Dick, and so easy to dance to!”)

I’m lost again in the rhythm until the technician asks me to bear down as if performing a common bodily function that polite people don’t talk about outside of hospital rooms. This seems a little strange, but who am I to question medical science?

“Um, OK.”

Suddenly, curiosity takes over and I ask why. She explains that this exercise, called the Valsalva maneuver, takes the pressure downward from the chest so the machine can read how the heart responds under less stress. “OK,” I say, satisfied. Then I ask how many patients pose the same question at this particular moment in the exam. She replies, “Only the smart ones.”

I’m momentarily flattered by the compliment until I realize that I, the ever-compliant health care consumer, would probably do anything and everything this woman told me to, thinking it was all part of the test. And I’m one of the smart ones?!

Then I start laughing out loud as I imagine the things a mischievous sonographer could make people do if she wanted to have some fun on a slow echocardiogram day. Raise their legs in the air, count to 10 in Spanish, pat their heads while rubbing their stomachs, sing the national anthem, whistle “Dixie,” wiggle their toes :

I am laughing so hard at the pictures in my head that the machine starts to go haywire. My heartbeat turns irregular: BAH-woomp, boomp, BEEP! BAH-woomp, beep, BEEP! The technician withdraws the cold steel wand and backs away from the table, alarmed.

“I think we’re all finished here,” she says in a deliberately soothing voice. “You can get dressed and go. “

“OK,” I say, still giggling like a madwoman. I head out the door to the crowded waiting room, smiling ear-to-ear with my shirt half-buttoned.

I am actually looking forward to humiliating midlife experience number 36.