Unable to retrieve heart rate reading and send to JY-MCU Bluetooth
assuming your circuit works, your code has some serious issues. I rewrote the code for you and also provided a simplified circuit that I have tested and know works.  Instead of getting the pulse from the heartbeat detector circuit, we will simulate it on the Arduino by pulsing pin 2 periodically. 

const int  signal = 7;    // Pin connected to the filtered signal from the circuit
unsigned long currentBeatTime;   
unsigned long previousBeatTime;

unsigned long frequency;

unsigned long myBeatFreq;
unsigned long myBeat;

// Internal variables
unsigned long period = 0;
int input = 0;
int lastinput = 0;


void setup() {
    pinMode(signal, INPUT);
    pinMode(2, OUTPUT);
    Serial.begin(9600);

    previousBeatTime = millis();
    myBeat = previousBeatTime;
}

void loop() {
    if ( millis()-myBeat &gt; myBeatFreq ) 
    {
      digitalWrite(2, HIGH);
      myBeat=millis();
    }
    else
    {
      digitalWrite(2, LOW);
    }

    input = digitalRead(signal);

    if ((input != lastinput) &amp;&amp; (input == HIGH)) {
        // If the pin state has just changed from low to high (edge detector)
        currentBeatTime = millis();

        period = currentBeatTime - previousBeatTime; // Compute the time between the previous beat and the one that has just been detected
        previousBeatTime = currentBeatTime; // Define the new time reference for the next period computing
    }

    lastinput = input; // Save the current pin state for comparison at the next loop iteration

    // Detect if there is no beat after more than 2 seconds
    if ( (millis() - previousBeatTime) &gt; 2000 ) 
    { 
        Serial.println("dead");
    }
    else 
    {
        if (period &lt;= 0) 
        {
            frequency = 0;
        }
        else 
        {
            frequency = 60000/period; // Compute the heart rate in beats per minute (bpm) with the period in milliseconds
        }

        Serial.print(frequency);
        Serial.println(" : alive! ");
    }
}